IPAC2015 - List of Keywords (impedance)

Paper	Title	Other Keywords	Page
MOAD1	Development of High Gradient RF System for J-PARC Upgrade	cavity, operation, proton, acceleration	50
	C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii KEK, Ibaraki, Japan M. Nomura, T. Shimada, F. Tamura, M. Yamamoto JAEA/J-PARC, Tokai-mura, Japan A. Schnase GSI, Darmstadt, Germany
	A new 5-cell cavity has been developed for the upgrade of the J-PARC Main Ring. In the cavity, high impedance magnetic alloy - Finemet FT3L, cores are loaded. The cavity was installed and has been used for the 250 kW beam operation. The cavity is operated with the RF voltage of 70 kV which is two times higher voltage than the present cavities. Eight more cavities will be assembled and installed in the next two years to increase the repetition rate of the Main Ring. This paper describes status of cavity operation under the beam loading and status of the mass productions of the cavities.
	Slides MOAD1 [2.551 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOAD1
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MOBD1	Preliminary Design of the High-Luminosity LHC Beam Screen with Shielding	vacuum, shielding, luminosity, cryogenics	60
	C. Garion, V. Baglin, R. Kersevan CERN, Geneva, Switzerland
	A new beam screen is needed in the High-Luminosity LHC (HL-LHC) final focusing magnets. Such an essential vacuum component, while operating in the range 40-60 K, has to ensure the vacuum performance and to prevent the beam-induced heating from reaching the cold bore which is at 1.9 K. In addition, they have to shield the cold mass from physics debris coming from the nearby beam collision points. To such purpose, energy absorbers made of tungsten alloy are installed onto the beam screen in the vacuum system. In this contribution, the proposed mechanical design is shown; it covers different thermomechanical aspects such as the behaviour during a magnet quench and the heat transfer from the tungsten absorbers to the cooling tubes. Assembly and manufacturing tolerances are also considered to evaluate the impact on the aperture. Results obtained with a short prototype assembly test are discussed.
	Slides MOBD1 [3.089 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD1
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MOBD3	Development of a 9 MHz 15 kW Solid-state CW Amplifier for RHIC	network, cavity, resonance, feedback	67
	S.C. Dillon Tomco Technologies, Stepney, South Australia, Australia
	This paper describes the technical details of the development of a high-power solid-state amplifier for Brookhaven Laboratory. The amplifier must withstand short duration events of 100% full-power reflection, and also must guarantee delivery of continuous power into any load impedance at any angle.
	Slides MOBD3 [10.800 MB]
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOBD3
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MOPWA001	Instability Thresholds and Tune Shift Estimation for Sirius	feedback, emittance, damping, simulation	70
	F.H. de Sá, L. Liu, N. Milas, X.R. Resende LNLS, Campinas, Brazil
	In this work we present the evaluation of longitudinal and transverse instability thresholds as well as tune shifts for Sirius using time and frequency domain codes that are being developed in-house and take into account various effects on the beam instability, such as bunch by bunch feedback system, quadrupolar impedances from undulator chambers and tune spreads.
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MOPWA018	Loss Factor and Impedance Analysis of Warm Components of BERLinPro	factory, simulation, operation, wakefield	128
	H.-W. Glock, M. Abo-Bakr, J. Kolbe, F. Pflocksch, A. Schälicke HZB, Berlin, Germany H.-W. Glock, C. Potratz COMPAEC e.G., Rostock, Germany
	Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association The ongoing component design for the HZB 50 MeV, 100mA ERL project BERLinPro is accompanied by loss factor and impedance computations. A list of accelerator components including bellows, collimators, tapers, shutter valves etc. is given, some of them with alternative shapes. Loss factors, calculated using CSTParticleStudio®, are presented together with important properties of the impedance spectrum. Scaling of the loss factors with respect to bunch length is calculated on base of the numerical simulations and is used to extrapolate down to a bunch length (1 standard deviation) of 0.6 mm, which is hard to reach directly in numerical simulations.
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MOPWA020	Longitudinal Stability Of Short Bunches in Storage Rings with Strong Longitudinal Focusing	synchrotron, dipole, simulation, resonance	135
	P. Kuske HZB, Berlin, Germany
	Funding: work supported by the BMBF In the BESSY VSR project, the variable bunch length storage ring, two high gradient accelerating structures at 1.5 and 1.75 GHz will be phased such that long and short bunches can be stored simultaneously. The longitudinal stability of the short bunches is investigated taking into account the shielded CSR- and a purely inductive impedance. Multi particle tracking studies and numerical solutions of the Vlasov-Fokker-Planck equation show that threshold currents for short bunches do not follow the simple scaling law which was found for long bunches. The inductive impedance can even lower the thresholds for the instability. With an 80 times increased accelerating gradient and reasonable assumptions on the inductive impedance for shorter bunches stable operation can be expected with bunches 1.8 ps long (RMS-value) and 0.8 mA current. According to the calculations and operating in a dedicated low-α mode will produce stable 40 μA bunches with 400 fs length
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MOPWA024	Estimation of the Ion Density in Accelerators using the Beam Transfer Function Technique	ion, electron, betatron, synchrotron	147
	D. Sauerland, W. Hillert ELSA, Bonn, Germany A. Meseck HZB, Berlin, Germany
	Funding: Funded by the federal ministry of education and science of Germany The ELSA stretcher ring of Bonn University serves external hadron physics experiments with a quasi continuous electron beam of up to 3.2 GeV energy. Ions, being generated by collisions of the circulating electrons with the residual gas molecules, accumulate inside the beam potential, causing incoherent tune shifts and coherent beam instabilities. Detailed measurements were carried out in which ion dynamics is studied in dependence of beam energy and current, filling patterns and bias voltages of the ion clearing electrodes. By measuring the beam transfer function using a broadband transversal kicker, we were able to derive an estimate of the average ion density from the shift and broadening of the tune peak. In this contribution first results of these measurements are presented.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA024
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MOPWA031	A New Approach for Resistive Wakefield Calculations in Time Domain	wakefield, simulation, cavity, controls	168
	A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland TEMF, TU Darmstadt, Darmstadt, Germany M. Dohlus, I. Zagorodnov DESY, Hamburg, Germany
	We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.
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MOPWA058	Measurement Results of the Impedance of the RF-cavity at the RCS in J-PARC	cavity, injection, kicker, proton	255
	Y. Shobuda, H. Harada, H. Hotchi JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	The kicker impedance dominates at the RCS in J-PARC. Recently, we observe beam instabilities, which are not explained by the kicker. As a candidate causing the beam instability, the impedance of the RF-cavity is measured. The longitudinal impedance is measured by stretching a single-wire inside the cavity. On the other hand, the measurement of the transverse impedance is done by horizontally shifting the single-wire, due to the accuracy problem. The measured impedance is too low to explain the beam instability.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPWA058
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MOPWA060	THE COUPLING IMPEDANCE MEASUREMENT OF THE FAST EXTRACTION KICKER IN CSNS/RCS *	kicker, coupling, extraction, proton	262
	L. Huang, Y.D. Liu, S. Wang IHEP, Beijing, People's Republic of China
	Rapid Cycling Synchrotron of the China Spallation Neutron Source is a high intensity proton accelerator. In order to high intensity beam operation, the beam coupling impedance of the extracted kickers must be controlled. The measurement of longitudinal and transverse coupling impedance of the extraction kicker is described. Supported by National Natural Science Foundation of China (11175193, 11275221)
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MOPJE026	Revision of the Impedance Model for the Interpretation of the Single Bunch Measurements at ALBA	vacuum, undulator, simulation, storage-ring	330
	T.F.G. Günzel, U. Iriso ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
	Recent measurements showed that the ALBA transverse impedance model was able to explain 65% of the measured single bunch vertical detuning. * This report shows the revision of the impedance model developed to match latest single bunch measurements performed to evaluate the total effective machine impedance and impedance of specific elements, like in-vacuum undulators or a recently installed pinger magnet. The model improvement includes a better bunch length parameterisation, re-calculation of several vacuum chamber elements with Gdfidl, and inclusion of elements neglected so far in the impedance budget. We also show and discuss the computation of the resistive wall impedance using ImpedanceWake2D. * T.Günzel, U.Iriso, F.Perez, E.Koukovini-Platia, G.Rumolo, "Analysis of the single bunch measurements at the ALBA Storage Ring", TUPRI052, proc. of IPAC14 (2014).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPJE026
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MOPJE027	Beam-based Impedance Characterization of the ALBA Pinger Magnet	simulation, vacuum, injection, synchrotron	334
	U. Iriso, T.F.G. Günzel ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain H. Bartosik, E. Koukovini-Platia, G. Rumolo CERN, Geneva, Switzerland
	The ALBA pinger magnet consists on two short kickers (for horizontal and vertical planes) installed in a single Titanium coated ceramic vacuum chamber. Single bunch measurements in the vertical plane were performed in the ALBA Synchrotron Light Source before and after the pinger installation, and by comparing the Transverse Mode Coupling Instability (TMCI) thresholds for zero chromaticity, we infer the pinger impedance and compare it with the model predictions. We also perform measurements for negative chromaticities and results are reported in this paper.
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MOPJE035	An Extended SPS Longitudinal Impedance Model	vacuum, kicker, simulation, resonance	360
	J.V. Campelo, T. Argyropoulos, T. Bohl, F. Caspers, J. F. Esteban Müller, J.B. Ghini, A. Lasheen, D. Quartullo, B. Salvant, E.N. Shaposhnikova, C. Zannini CERN, Geneva, Switzerland
	Longitudinal multi-bunch instability in the CERN SPS with a very low intensity threshold is a serious limitation for the future doubling of bunch intensity required by Hi-Lumi LHC project. A complete and accurate impedance model is essential to understand the nature of this instability and to plan possible cures. This contribution describes in detail the current longitudinal impedance model of the SPS. Recently, the model was updated with new findings and includes now the impedance of accelerating cavities, kicker and septum magnets, beam position monitors, vacuum Flanges, shielded and unshielded pumping ports, electrostatic septa and resistive wall. Electromagnetic simulations and bench measurements were used to build the model. The contribution from each element is described and compared to the total machine impedance. Together with relevant beam measurements and simulations, the analysis of the different sources of impedance is used to identify the source of the longitudinal instability limiting the SPS performance so that the responsible elements can be acted upon.
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MOPJE036	Longitudinal Impedance Characterization of the CERN SPS Vacuum Flanges	resonance, vacuum, simulation, damping	363
	J.V. Campelo CERN, Geneva, Switzerland
	This contribution describes the thorough studies carried out to characterize the longitudinal impedance of the CERN SPS vacuum flanges, which are believed to be the main source of LHC beam instability. Around 500 high-impedance flanges of 8 different types have been identified. Three factors play an important role in the characterization of these flanges: the type of vacuum chambers that the flange interconnects, whether or not both sides are electrically isolated (by means of an enamel coating) and, finally, the presence of damping resistors which damp high-Q resonances. Not only, full-wave electromagnetic field simulations, but also RF measurements have been used to evaluate the impedance of these elements. The R/Q of the relevant resonances was measured using the well-known bead-pull technique. In particular, a subset of around 150 flanges has been found to be the source of a high-impedance resonance at 1.4 GHz, also observed in beam measurements. Guidelines on how to reduce the impedance of these elements are also presented.
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MOPJE038	Impedance Studies of the LHC Injection Kicker Magnets for HL-LHC	coupling, kicker, injection, simulation	370
	H.A. Day, M.J. Barnes, L.M.C. Feliciano CERN, Geneva, Switzerland
	The LHC injection kicker magnets (MKIs) experienced strong heating during the first operational run, identified as being caused by power loss due to wakefields induced by stored beam. Studies of the beam coupling impedance of the beam screen, a series of conductors embedded in a ceramic tube placed in the ferrite yoke to screen the ferrite from the beam, resulted in new design offering improved screening: this is predicted to reduce the heating to acceptable levels for operation with 25ns beam during Run 2 of the LHC. However higher beam intensities proposed for HL-LHC operation are predicted to again cause strong heating to occur. Further studies have been carried out to reduce the beam induced power loss by optimising the beam screen design, some key results and findings of which are presented here.
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MOPJE047	Chromaticity Dependence of the Transverse Effective Impedance in the CERN Proton Synchrotron	proton, synchrotron, controls, space-charge	395
	S. Persichelli, N. Biancacci, S.S. Gilardoni, A. Huschauer, E. Métral, B. Salvant, R. Wasef CERN, Geneva, Switzerland M. Migliorati University of Rome La Sapienza, Rome, Italy
	The current knowledge of the transverse impedance of the Proton Synchrotron (PS) has been established with beam-based measurements at different energies. The transverse coherent tune shift as a function of the beam intensity has been measured in order to evaluate the total effective imaginary part of the transverse impedance and its localization in the accelerator at the energies of 2, 7, 13 and 25 GeV. Measurements have been performed changing the chromaticity for every tune shift scan with intensity. The data analysis revealed an increase of impedance with chromaticity for all the energies considered. That transverse impedance can be compared with the previously evaluated theoretical impedance budget taking into account the individual contribution of several machine devices. The missing impedance is finally highlighted.
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MOPJE049	Benchmarking the CERN-SPS Transverse Impedance Model with Measured Headtail Growth Rates	simulation, kicker, optics, vacuum	402
	C. Zannini, H. Bartosik, G. Iadarola, G. Rumolo, B. Salvant CERN, Geneva, Switzerland
	The latest SPS transverse impedance model includes kicker magnets, wall impedance, transition pieces (e.g. flanges and vacuum chamber discontinuities), beam position monitors and RF cavities. The model has already been successfully benchmarked against coherent tune shift and transverse mode coupling instability measurements. In this paper we present measurements of the headtail growth rates for a wide range of negative chromaticities and for two different configurations of machine optics (nominal and low gamma transition). The measurement results are compared with HEADTAIL simulations using the wake fields obtained from the SPS transverse impedance model.
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MOPJE050	Transverse Impedance Model of the CERN-PSB	space-charge, kicker, simulation, vacuum	406
	C. Zannini, G. Iadarola, K.S.B. Li, T.L. Rijoff, G. Rumolo CERN, Geneva, Switzerland B. Jones STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom T.L. Rijoff TU Darmstadt, Darmstadt, Germany
	In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices before installation in the machine. This paper describes the PSB impedance model which includes resistive wall, indirect space charge, flanges, step transitions, ejection kicker including cables, injection kickers and cavities. Each impedance contribution has been computed for different energies in the PSB cycle. Measurements of the coherent tune shifts have been performed and compared to calculations based on the impedance model.
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MOPJE064	Beam Impedance Optimization of the TOTEM Roman Pots	detector, simulation, cavity, vacuum	452
	N. Minafra CERN, Geneva, Switzerland
	The TOTEM experiment has been designed to measure the total proton-proton cross section and to study elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots (RP), special beam pipe insertions, to move silicon detectors close to the beams to detect particles very near the beam axis. In the first period of running of the LHC no problems were detected with retracted Roman Pots and during insertions in special runs; however, during close insertions to highest intensity beam, impedance heating has been observed. After the LS1 the LHC beam current will increase and the equipment that can interact with the beam needed to be optimized. A new RP, optimized to minimize the beam coupling, has been designed with the help of CST Particle Studio; a prototype has been used to test the simulation results in the laboratory with wire and probe measurements. Furthermore, in both the old and the new RPs, new ferrites have been installed. The new ferrite material has a higher Curie temperature than the one used before LS1 and a thermal treatment at 1000°C has been applied to reduce the out-gassing.
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MOPJE072	Simulations and Measurements of Longitudinal Coupled-bunch Instabilities in the CERN PS	feedback, cavity, synchrotron, luminosity	479
	L. Ventura, H. Damerau, M. Migliorati, G. Sterbini CERN, Geneva, Switzerland M. Migliorati, L. Ventura INFN-Roma1, Rome, Italy M. Migliorati University of Rome La Sapienza, Rome, Italy L. Ventura University of Rome "La Sapienza", Rome, Italy
	Among various and challenging objectives of the LHC Injectors Upgrade project (LIU), one aim is to double the beam intensity of the CERN Proton Synchrotron (PS) in order to achieve the integrated luminosity target of the High-Luminosity LHC project (HL-LHC). A known limitation to reach the required high intensity is caused by the longitudinal coupled-bunch oscillations developing above the transition energy. The unwanted oscillations induce large bunch-to-bunch intensity variations not compatible with the specifications of the future LHC-type beams. A wide-band longitudinal damper has been installed in the PS to suppress these instabilities and is going to be commissioned. A measurement campaign of coupled-bunch oscillations has been launched to substantiate the extrapolations and predictions for the future High Luminosity LHC beam with the final aim to determine the maximum intensity that could be provided to the LHC. In parallel a Simulink© model of the PS is going to be implemented to predict the machine behavior in the parameter space of LIU and to be used during the beam commissioning and optimization of the feedback system.
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MOPMA001	Comparison of Measurements and Simulations for Single Bunch Instabilities at Diamond	wakefield, radiation, simulation, synchrotron	521
	M. Atay, R. Bartolini JAI, Oxford, United Kingdom R. Bartolini, R.T. Fielder, I.P.S. Martin DLS, Oxfordshire, United Kingdom
	The single bunch dynamics in the Diamond storage ring has been analysed with a multiparticle tracking code and compared with the results of a wealth of diagnostics, including streak camera, Schottky diodes and FTIR spectra. The interplay of various wakefield sources has been studied and it has been found that the THz spectrum can be reproduced in many cases with simple impedance models, both below and above the bursting threshold.
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MOPMA006	Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade	feedback, cavity, injection, storage-ring	540
	T.G. Berenc, M. Borland ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice includes a passive bunch-lengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.
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MOPMA007	Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade	simulation, cavity, feedback, timing	543
	M. Borland, T.G. Berenc, R.R. Lindberg, A. Xiao ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.
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MOPMA009	Improvements in Modeling of Collective Effects in ELEGANT	simulation, cavity, collective-effects, lattice	549
	M. Borland, R.R. Lindberg, A. Xiao ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.
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MOPMA025	CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs	dipole, lattice, simulation, damping	596
	C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA D. Douglas, R. Li, C. Tennant JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.
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MOPMA040	Analysis of Beam Transverse Instabilities at Fermilab	dipole, space-charge, coupling, quadrupole	633
	T. Zolkin University of Chicago, Chicago, Illinois, USA
	The transverse beam dynamics in Fermilab Recycler ring has been analyzed using SCHARGEV Vlasov solver. In the first part of paper we discuss how SCHARGEV analyses collective instabilities for Gaussian bunch with strong space charge in resistive impedance environment. In the second part the bunched beam dynamics is studied depending on head-tail phase and damper gain. An example for Fermilab Recycler is presented.
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MOPMA056	Measurement and Modeling of Single Bunch Wake Field Effects in CESR	emittance, simulation, wakefield, storage-ring	681
	J.R. Calvey, M.G. Billing, W. Hartung, J.D. Perrin, D. L. Rubin, D. Sagan, S. Wang Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work supported by NSF PHY-1416318 and NSF DMR 1332208. This research used the National Energy Research Scientific Computing Center, which is supported by DOE Contract No. DE-AC02-05CH11231. Short-range wake fields have been incorporated into a Bmad-based particle tracking code in order to assess their contribution to current-dependent emittance growth, tune shift, and single bunch instabilities. The wakes are computed for CESR vacuum components using the T3P modeling software. Simulation results are compared with measurements of bunch length, vertical beam size, and coherent tune shift. Additionally, we use insertable scrapers to vary the transverse wake and measure the effect on the beam. We show that a vertical emittance increase at high current may be due to a transverse monopole wake, originating in the lump pump slots throughout CESR.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2015-MOPMA056
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MOPMA060	Impedance Measurement for the SPEAR3 Storage Ring	lattice, storage-ring, vacuum, damping	694
	X. Huang, J.J. Sebek SLAC, Menlo Park, California, USA
	We studied the transverse impedance of the SPEAR3 storage ring with tune shift vs. beam intensity, head-tail instability and transverse mode coupling instability measurements. By taking measurements under different machine conditions, we probed the frequency dependence of the impedance, from which an impedance model was built. This model is consistent with instability measurements and previous bunch lengthening results.
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MOPMN004	CSR Impedance for Non-Ultrarelativistic Beams	wakefield, radiation, space-charge, synchrotron	709
	R. Li JLab, Newport News, Virginia, USA C.-Y. Tsai Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
	Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. For the analysis of the coherent synchrotron radiation (CSR) induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.
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MOPMN019	Understanding the Effect of Space Charge on Instabilities	space-charge, synchrotron, hadron, operation	743
	M. Blaskiewicz BNL, Upton, Long Island, New York, USA A. Chao SLAC, Menlo Park, California, USA Y.H. Chin KEK, Ibaraki, Japan
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The combined effects of space charge and wall impedance on transverse instabilities is an important consideration in the design and operation of hadron machines as well as an intrinsic academic interest. This study explores the combined effects of space charge and wall impedance using various simplified models in an attempt to produce a better understanding of their interplay.
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MOPMN020	Longitudinal Impedance of RHIC	synchrotron, experiment, storage-ring, scattering	746
	M. Blaskiewicz, J.M. Brennan, K. Mernick BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. With Z/n about 5 Ω the impedance of the yellow ring is roughly twice that of the blue ring.
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MOPMN021	NSLS-II Storage Ring BPM Button Development	vacuum, simulation, multipole, storage-ring	748
	A. Blednykh, B. Bacha, G. Bassi, W.X. Cheng, C. Hetzel, B.N. Kosciuk, D. Padrazo, O. Singh BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE contract DE-AC02-98CH10886 The NSLS-II BPM Button design and its development process have been described. Subjects discussed include BPM Button impedance optimization, design and construction, production, BPM Button selection and a first temperature measurements at 200mA average current within 1200 bunches.
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MOPMN025	Local Impedance Estimation of NSLS-II Storage Ring with Bumped Orbit	closed-orbit, wiggler, damping, vacuum	754
	J. Choi, G. Bassi, A. Blednykh, Y. Hidaka BNL, Upton, Long Island, New York, USA
	Funding: DOE contract No: DE-AC02- 98CH10886 As the newly constructed 3rd generation light source, NSLS-II is expected to provide the synchrotron radiation of ultra high brightness and flux with advanced insertion devices. To minimize the beam emittance, damping wigglers are used and the small aperture is located at the straight section with the damping wiggler and the corresponding vacuum camber is NEG coated. We used the local bump method to find the effect on the beam from the narrow aperture and the paper shows the results.
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MOPTY001	Development of Wideband BPM for Precise Measurement of Internal Bunch Motion	coupling, feedback, synchrotron, network	937
	K.G. Nakamura Kyoto University, Kyoto, Japan Y.H. Chin, T. Koseki, T. Obina, M. Okada, M. Tobiyama, T. Toyama KEK, Ibaraki, Japan Y. Shobuda JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan
	Funding: This work was supported by MEXT KAKENHI Grant Number 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled “ Unification and　Development of the Neutrino Science Frontier” To suppress intra-bunch oscillations and to reduce particle losses, the intra-bunch feedback (IBFB) system has been developed in 2014 for the J-PARC Main Ring (MR). A new BPM was also installed to the MR for the IBFB system. This BPM has a sufficient frequency response and position sensitivity(up to 1.5GHz within 15% fluctuation ). However, a better performance may be needed in future for more precise analysis of internal motions (e.g. due to an electron cloud). We report the development of the BPM and precise measurement results of the BPM characteristics. We also report simulation studies of the digital equalizer which helps to reconstructs the beam shape from beam signals.
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MOPTY019	Precise Position Measurement by Analyzing the Correlation Between Electrodes of a Single Bpm	simulation, pick-up, hardware, synchrotron	975
	Z.C. Chen SSRF, Shanghai, People's Republic of China L.W. Lai, Y.B. Leng, Y.B. Yan SINAP, Shanghai, People's Republic of China
	Beam position is one of the most important parameters in a particle accelerator. The more accurate and precise the measurement system is, the more features of the beam dynamics could be revealed. A method called model-independent analysis (MIA) takes advantage of multiple beam position monitors (BPM) on the storage ring to obtain the actual beam positions by removing the random noise of each BPM. Inspired by MIA, the original voltage waveforms obtained from the electrodes of a single BPM can also be decomposed to get the beam position information. This article discusses the results of the experiments and the evaluation of the performance of the BPM at the Shanghai Institute of Applied Physics.
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MOPTY033	Fast Kicker	kicker, simulation, vacuum, magnet-design	1001
	V.V. Gambaryan, A.A. Starostenko BINP SB RAS, Novosibirsk, Russia
	Pulsed deflecting magnet project was worked out in BINP. The kicker design task is: impulsive force value is 1 mT*m, pulse edge is 5 ns, and impulse duration is about 200 ns. The unconventional approach to kicker design was offered. The possibility for set of wires using instead of plates using is considered. This approach allows us to reduce the effective plate surface. In this case we can decrease effects related to induced charges and currents. In the result of modelling optimal construction was developed. It includes 6 wires. The magnet aperture is about 5 cm. Calculated field rise time (about 1.5 ns) satisfies the conditions. Induced current effect reducing idea was confirmed. For configuration with 3 wires pair (with cross section of 2 mm) induced current in one wire is about 10% and in the wall is about 40%. However for design with plates current is about 40% and 20% respectively. Obtained magnet construction allows controlling of high field homogeneity by changing currents magnitudes in wires. In general we demonstrated the method of field optimization. Optimal kicker design was obtained. Wires using idea was substantiated.
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MOPTY041	Prototype Results with a Complete Beam Loss Monitor System Optimized for Synchrotron Light Sources	electron, detector, injection, electronics	1019
	P. Leban I-Tech, Solkan, Slovenia K.B. Scheidt ESRF, Grenoble, France
	Beam loss monitors in synchrotron light sources are finding an increasing utility in particular with the trend of numerous light sources pushing to lower emittances and thus higher intra-beam scattering, while operating in top-up injection modes and employing in-vacuum undulators in their rings. The development of an optimized electron BeamLoss Monitor aims at fulfilling, in one single system, all possible functionalities and applications like both the measurement of fast-time-resolved losses at injection and the possibility of ultra-sensitive detection of low & slow electron loss level variations. This optimized beam loss monitor system comprises both the acquisition electronics and up to four sensor head per unit. The sensor heads themselves, that can be configured for different sizes or volumes, are based on the detection of the electromagnetic shower resulting from an electron loss through the use of either Cherenkov radiator or gamma scintillator and a photomultiplier tube, all assembled in a single compact housing ready for installation.
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MOPTY053	Electromagnetic Design and Optimization of Directivity of Stripline Beam Position Monitors for the High Luminosity Large Hadron Collider	luminosity, simulation, hadron, collider	1051
	D. Draskovic, C.B. Boccard, O.R. Jones, T. Lefèvre, M. Wendt CERN, Geneva, Switzerland
	This paper presents the preliminary electromagnetic design of a stripline Beam Position Monitor (BPM) for the High Luminosity program of the Large Hadron Collider (HL-LHC) at CERN. The design is fitted into a new octagonal shielded Beam Screen for the low-beta triplets and is optimized for high directivity. It also includes internal Tungsten absorbers, required to reduce the energy deposition in the superconducting magnets. The achieved broadband directivity in wakefield solver simulations presents significant improvement over the directivity of the current stripline BPMs installed in the LHC.
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MOPWI012	Conceptual Design and Analysis of a Storage Ring Beam Position Monitor for the APS Upgrade	vacuum, operation, simulation, alignment	1170
	B.K. Stillwell, R.M. Lill, R.R. Lindberg, M.M. O'Neill, B.G. Rocke, X. Sun ANL, Argonne, Ilinois, USA A. Blednykh BNL, Upton, Long Island, New York, USA
	Funding: Created by UChicago Argonne, LLC, operator of Argonne National Laboratory, a U.S. Department of Energy Office of Science laboratory operated under Contract No. DE-AC02-06CH11357. A conceptual design has been developed for a radio frequency (rf) pickup-type beam position monitor (BPM) for use in a multi-bend achromat (MBA) storage ring under consideration by the APS Upgrade project (APS-U). Beam feedback systems are expected to require fourteen rf BPMs per sector with exceptional sensitivity and mechanical stability. Simultaneously, BPM insertion length must be minimized to allow lattice designers the greatest freedom in selecting magnet lengths and locations. Envisioned is a conventional four probe arrangement integrated inside of a pair of rf-shielded bellows for mechanical isolation. Basic aspects of the design are presented along with the results of analyses which establish expected mechanical, electronic, and beam physics-related performance measures.
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TUAB2	First Collective Effects Measurements in NSLS-II with ID's	lattice, vacuum, quadrupole, storage-ring	1332
	A. Blednykh, B. Bacha, G. Bassi, W.X. Cheng, J. Choi, Y. Hidaka, Y. Li, B. Podobedov, T.V. Shaftan, V. Smalyuk, T. Tanabe, G.M. Wang, F.J. Willeke, L.-H. Yu BNL, Upton, Long Island, New York, USA
	Funding: Work supported by DOE contract DE-AC02-98CH10886. As another important milestone towards the final goal to store an average current of 500mA, the average current of 200mA, distributed within ~1000 bunches, was recently achieved in the NSLS-II storage ring after the installation of three Damping Wigglers and four In-Vacuum Undulators. First measurements of the collective effects and instability thresholds, both in single- and multi-bunch mode, are discussed.
	Slides TUAB2 [2.691 MB]
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TUPJE065	Multi-Bunch Stability Analysis of the Advanced Photon Source Upgrade Including the Higher-Harmonic Cavity	HOM, damping, simulation, radiation	1784
	L. Emery, T.G. Berenc, M. Borland, R.R. Lindberg ANL, Argonne, Ilinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357 Multi-bunch stability simulations were done for the very-low-emittance hybrid seven-bend-achromat (H7BA) lattice proposed for the Advanced Photon Source (APS) upgrade. The simulations, performed using tracking code elegant, were meant to determine whether the long-term wakefields of the higher-order modes (HOMs) of the main 352-MHz cavities will produce an instability. The multi-particle simulations include the important effects of the Higher-Harmonic Cavity (HHC) and the longitudinal impedance of the new vacuum chamber. These realistic simulations show that the HHC provides additional damping in the form of the Landau damping. Still, the HOMs may likely produce a multi-bunch instability which can be cured with more effective HOM damping or a longitudinal feedback system.
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TUPJE069	Fast Injection System R&D for the APS Upgrade	kicker, high-voltage, injection, extraction	1797
	F. Lenkszus, J. Carwardine, A.R. Cours, G. Decker, L.H. Morrison, X. Sun, J. Wang, F. Westferro, A. Xiao, C. Yao ANL, Argonne, Ilinois, USA A. Krasnykh SLAC, Menlo Park, California, USA
	Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357. The MBA upgrade for the APS will operate with bunch swap out and on axis injection. The planned 324 bunch fill pattern places difficult demands on the injection and extraction kickers. The present concept uses dual stripline kickers driven by high Voltage pulsers. Minimizing perturbation on adjacent bunches requires very fast rise and fall times with relatively narrow ~20 nsec, 15 kV pulses. To achieve these requirements we have initiated a multifaceted R&D program. The R&D includes the HV pulser, stripline kicker and HV feedthrough. We have purchased a commercial dual channel HV pulser and are evaluating its performance and reliability. In addition, we are investigating the feasibility of using nonlinear ferrite loaded coaxial cables (shockwave transmission line) to sharpen the leading and trailing edges of high voltage pulses. We are also developing a prototype kicker and high voltage feedthrough. The requirements for injection and extraction, progress on prototype development and results of our HV pulser investigations will be reported.
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TUPJE076	Design Study of the Higher Harmonic Cavity for Advanced Photon Source Upgrade	cavity, operation, simulation, superconducting-cavity	1819
	S.H. Kim, T.G. Berenc, J. Carwardine, G. Decker, M.P. Kelly, P.N. Ostroumov ANL, Argonne, Illinois, USA
	Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357. A higher-harmonic cavity is planned for the proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice to increase the bunch length, improve the Touschek lifetime and increase the single-bunch current limit. We have investigated a range of options including 3rd, 4th, and 5th harmonics of the main radio frequency (RF) system, as well as configurations with and without external RF power couplers. The current baseline is a single 4th harmonic superconducting cavity with adjustable RF couplers and a slow tuner which provide the flexibility to operate over a wide range of beam currents. The cavity is designed to provide 0.84 MV at 1408 MHz for the nominal 6 GeV, 200 mA electron beam, and 4.1 MV main RF voltage. In this paper, we discuss the harmonic cavity parameters based on analytical calculations of the equilibrium bunch distribution and make comparisons to other options.
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TUPJE077	Instability Thresholds for the Advanced Photon Source Multi- Bend Achromat Upgrade	simulation, wakefield, injection, collective-effects	1822
	R.R. Lindberg ANL, Argonne, Illinois, USA A. Blednykh BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. An important operating mode for the multi-bend achromat (MBA) upgrade at the Advanced Photon Source (APS) calls for 200 mA average current divided evenly over 48 bunches. Ensuring that the desired 4.2 mA single bunch current can be stably stored requires a detailed understanding of the impedance in the MBA ring. We briefly discuss modeling sources of impedance using the electromagnetic codes GdfidL and ECHO, and how we then include both geometric and resistive wall wakefields using the tracking code elegant to predict collective instabilities. We first validate our procedures by comparing APS experimental measurements to tracking predictions using the APS storage ring impedance model. We then discuss the MBA impedance model, for which we find that a chromaticity of 5 units is sufficient to obtain the required 4.2 mA single bunch current. Finally, we mention certain design changes that may reduce the impedance and allow for a reduction in chromaticity.
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TUPJE078	Modeling of Impedance Effects for the APS-MBA Upgrade	vacuum, wakefield, photon, simulation	1825
	R.R. Lindberg ANL, Argonne, Illinois, USA A. Blednykh BNL, Upton, Long Island, New York, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. Understanding the sources of impedance is critical to accelerator design, and only becomes more important as vacuum chambers become smaller and closer to the electron beam. The multibend achromat upgrade at the Advanced Photon Source (APS) requires small, 22-mm diameter vacuum chambers and even smaller (6 mm) gaps for the insertion devices, so that both rf heating and wakefield-driven transverse instabilities become important concerns. We discuss modeling the primary sources of geometric impedance using the electromagnetic finite difference codes GdfidL and ECHO, and how these codes are influencing vacuum and accelerator component design.
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TUPJE079	High Charge Development of the APS Injector for an MBA Upgrade	booster, vacuum, ion, injection	1828
	C. Yao, M. Borland, J.R. Calvey, K.C. Harkay, D. Horan, R.R. Lindberg, N. Sereno, H. Shang, X. Sun, J. Wang ANL, Argonne, Illinois, USA
	Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The APS MBA (multi-bend achromat) upgrade storage ring will employ a “swap out” injection scheme and requires a single-bunch beam with up to 20 nC from the injector. The APS injector, which consists of a 450-MeV linac, a particle accumulator ring (PAR), and a 7-GeV synchrotron (Booster), was originally designed to provide up to 6 nC of beam charge. High charge injector study is part of the APS upgrade R&D that explores the capabilities and limitations of the injector through machine studies and simulations, and identifies necessary upgrades in order to meet the requirements of the MBA upgrade. In the past year we performed PAR and booster high charge studies, implemented new ramp correction of the booster rap supplies, explored non-linear chromatic correction of the booster, etc. This report presents the results and findings.
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TUPMA007	Numerical Investigation of a Cascaded Longitudinal Space-Charge Amplifier at the Fermilab's Advanced Superconducting Test Accelerator	space-charge, radiation, bunching, simulation	1850
	A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA P. Piot Fermilab, Batavia, Illinois, USA
	In a cascaded longitudinal space-charge amplifier (LSCA), initial density noise in a relativistic e-beam is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. This type of amplification process was shown to potentially result in large final density modulations * compatible with the production of broadband electromagnetic radiation. The technique was recently demonstrated in the optical domain *. In this paper we investigate, via numerical simulations, the performances of a cascaded LSCA beamline at the Fermilab's Advanced Superconducting Test Accelerator (ASTA). We especially explore the properties of the produced broadband radiation. Our studies have been conducted with an effective three-dimensional space-charge algorithm. Dohlus, M. et al. Proc. SPIE 8779. doi:10.1117/12.2017369 ** Marinelli, A. et al. Phys. Rev. Lett. 110, 264802 (2013)
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TUPMA008	Numerical Study of Three Dimensional Effects in Longitudinal Space-Charge Impedance	space-charge, simulation, detector, radiation	1853
	A. Halavanau, P. Piot Northern Illinois University, DeKalb, Illinois, USA P. Piot Fermilab, Batavia, Illinois, USA
	Longitudinal space-charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed instabilities. Such "microbunching instabilities" were recently shown to be potentially useful to support the generation of broadband coherent radiation pulses. Therefore there has been an increasing interest in devising accelerator beamlines capable of sustaining this LSC instability as a mechanism to produce a coherent light source. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. In this paper we use a N-body "Barnes-Hut" algorithm * to simulate the 3D space charge force in the beam combined with Elegant ** and explore the limitation of the 1D model often used. * Barnes, J. & Hut, P., Nature 324, 446-449, 1986. ** Borland, M., Advanced Photon Source LS-287, 2000.
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TUPMA041	On the Characterization of a CCR Source	brightness, radiation, FEL, emittance	1926
	A.V. Smirnov RadiaBeam, Santa Monica, California, USA
	Funding: US Department of Energy, contract # DE- SC-FOA-0000760 Peak and spectral brightness of a resonant long-range wakefield extractor are evaluated. It is shown that the brightness is dominated by beam density within the slow wave structure and antenna gain of the outcoupling. Far field radiation patterns and brightness of circular and high-aspect-ratio planar radiators are compared. A possibility to approach the diffraction limited brightness is demonstrated. Role of group velocity in designing of the Cherenkov source is emphasized. The approach can be applied for design and characterization of various structure-dominated sources (e.g., wakefield extractors with gratings or dielectrics, or FEL-Cherenkov combined sources) radiating into a free space using an antenna (from microwave to far infra-red regions). The high group velocity structures can be also effective as energy dechirpers and for diagnostics of microbunched relativistic electron beams.
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TUPTY029	Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials	collimation, simulation, scattering, proton	2068
	E. Quaranta, R. Bruce, A. Mereghetti, S. Redaelli, A. Rossi CERN, Geneva, Switzerland
	The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.
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TUPTY038	BPM Tolerances for HL-LHC Orbit Correction in the Inner Triplet Area	luminosity, optics, simulation, emittance	2094
	M. Fitterer, R. De Maria CERN, Geneva, Switzerland
	Funding: The HiLumi LHC Design Study is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404. For the HL-LHC beam spot sizes as small as 7 mum are considered for the high luminosity insertions IR1 and IR5. In addition, the luminosity has to be levelled over several hours by changing β^* resulting in constant changes of the optics and thus orbit changes. The small beam size and the continuous optics changes in general make the alignment of the beams at the IP challenging. In order to avoid continuous luminosity scans for the alignment of the beams at the IP, the orbit correction has to rely on the readings of the BPMs in the IT region. In this paper we review the requirements on resolution and accuracy of the BPMs and compare different options for the placement of the BPMs in the IT region.
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TUPTY051	Injection Protection Upgrade for the HL-LHC	injection, simulation, kicker, proton	2136
	J.A. Uythoven, N. Biancacci, C. Bracco, L. Gentini, B. Goddard, A. Lechner, F.L. Maciariello, A. Perillo Marcone, B. Salvant, N.V. Shetty, G.E. Steele, F.M. Velotti CERN, Geneva, Switzerland O. Frasciello, M. Zobov INFN/LNF, Frascati (Roma), Italy
	The injector complex of the LHC is undergoing important changes in the light of the LIU project to provide brighter beams to the LHC. For this reason and as part of the High Luminosity LHC project the injection protection system of the LHC will be upgraded in the Long Shutdown 2 (2018 - 2019) to be able to protect downstream elements against injection failures with the high brightness, high intensity HL-LHC beams. The upgraded LHC injection protection system will consist of a segmented injection protection absorber TDIS, and auxiliary collimators and masks. The layout modifications are described, and the machine element protection and absorber jaw robustness studies are presented for the new systems.
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WEPWA046	Time Domain Simulations of Detuned Accelerating Cavities for Two Beam Applications	cavity, simulation, accelerating-gradient, cathode	2605
	R.M. Jones, L.R. Carver UMAN, Manchester, United Kingdom
	A multi-harmonic accelerating cavity that has its fundamental and harmonic mode frequency detuned away from the bunch repetition frequency could provide the basis for a beam driven wakefield accelerator with high transformer ratios. The excitation of multiple harmonic eigenmodes will allow high gradients to be achieved without encouraging the onset of rf breakdown or pulsed surface heating. This accelerating cavity will be introduced, and time domain simulations verifying the theory will be shown.
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WEPMA008	RF Design of a High Gradient S-Band Travelling Wave Accelerating Structure for Thomx Linac	accelerating-gradient, linac, simulation, vacuum	2757
	M. El Khaldi, L. Garolfi LAL, Orsay, France
	There is growing demand from the industrial and research communities for high gradient, compact RF accelerating structures. The Thomx high gradient structure (HGS) is travelling wave (TW), quasi constant gradient section and will operate at 2998.55 MHz (30°C in vacuum) in the 2π/3 mode. The optimization of the cell shape (Electromagnetic design) has been carried out with the codes HFSS and CST MWS, in order to improve the main RF characteristics of the cavity such as shunt impedance, accelerating gradient, group velocity, modified Poynting vector, surface fields, etc. Prototypes with a reduced number of cells have been designed. For an input power of about 20 MW, EM simulation results show that an average accelerating gradient of 28 MV/m is achieved which corresponds to a peak accelerating gradient of 35 MV/m, a peak surface gradient of 44 MV/m and peak modified Poynting vector S_cmax of 0.24 MW/mm².
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WEPMA013	Hom Damping Optimization Design Studies for BESSY VSR Cavities	damping, HOM, cavity, SRF	2774
	A.V. Vélez, H.-W. Glock, J. Knobloch, A. Neumann HZB, Berlin, Germany
	The BESSY VSR project is a future upgrade of the 3rd generation BESSY II light source. By using the same "standard" user optics, simultaneously long (ca. 15ps) and short (ca. 1.5ps) bunches will be stored. Thus, superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. This work describes the optimizations studies for the Waveguide-based HOM dampers and the adjustable fundamental power coupler for the 1.5 GHz first SRF cavity prototype.
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WEPMA017	Alvarez DTL Cavity Design for the UNLAC Upgrade	cavity, electron, DTL, simulation	2786
	X. Du, L. Groening, S. Mickat GSI, Darmstadt, Germany A. Seibel IAP, Frankfurt am Main, Germany
	The 10⁸.4 MHz drift tube linac (DTL) accelerator for GSI’s UNLAC upgrade project is in its initial design stage using CST-MWS code. Optimization criteria for cavity design are effective shunt impedance (ZTT), transit-time factor, and electrical breakdown limit. In geometrical op-timization we have aimed at increase of the energy gain in each RF gap of the DTL cells by maximizing ZTT per peak surface field with special designed tube profile. Mul-ti-pacting probability is evaluated for one gap of typical single cell. For the beta profile design, a code based on VBA macros of CST is developed to perform cell by cell design with pre-optimized 3D tube structures. With this code several beta profile designs are presented and com-pared for the balance of power consumption, ZTT, tank length, and breakdown possibility of the complete cavity. The stability of the field has been taken into account and for this the crossed stem arrangement is assessed. This paper gives a short introduction of the method, presents some important results. Possible countermeas-ures are discussed.
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WEPMN012	Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun	cathode, cavity, gun, electron	2940
	P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu PKU, Beijing, People's Republic of China
	Funding: Work supported by National Basic Research Project (No. 2011CB808302) The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.
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WEPMN025	Harmonic Resonant Kicker Design for the MEIC Electron Circular Cooler Ring	cavity, electron, kicker, ion	2981
	Y.L. Huang IMP/CAS, Lanzhou, People's Republic of China R.A. Rimmer, H. Wang, S. Wang JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177. Bunched-beam electron cooling of the high-energy ion beam emittance may be a crucial technology for the proposed Medium energy Electron Ion Collider (MEIC) to achieve its design luminosity. A critical component is a fast kicker system in the Circular Ring (CR) that periodically switches electron bunches in and out of the ring from and to the driver Energy Recovery Linac (ERL). Compared to a conventional strip-line type kicker, a quarter wave resonator (QWR) based deflecting structure has a much higher shunt impedance and so requires much less RF power. The cavity has been designed to resonate simultaneously at many harmonic modes that are integer multiples of the fundamental mode. In this way the resulting waveform will kick only a subset of the circulating bunches. In this paper, analytical shunt impedance optimization, the electromagnetic simulations of this type of cavity, as well as tuner and coupler concept designs to produce 5 odd and 5 even harmonics of 47.63MHz will be presented, in order to kick every 10th bunch in a 476.3 MHz bunch train.
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WEPMN047	Suppression of Higher Order Modes in an Array of Cavities Using Waveguides	HOM, damping, cavity, wakefield	3033
	Ya.V. Shashkov, N.P. Sobenin MEPhI, Moscow, Russia M. Zobov INFN/LNF, Frascati (Roma), Italy
	Funding: Work is supported by Ministry of Education and Science grant 3.245.2014/r и and by the EU FP7 HiLumi LHC - Grant Agreement 284404 In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussion. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between “warm” and “cold” parts of the collider vacuum chamber. Unfortunately it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. In this paper we describe the results obtained for arrays of 2, 4 and 8 cavities.
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WEPMN058	Transverse Impedance Measurements and DC Breakdown Tests on the First Stripline Kicker Prototype for the CLIC Damping Rings	simulation, coupling, kicker, extraction	3058
	C. Belver-Aguilar, A. Faus-Golfe IFIC, Valencia, Spain M.J. Barnes, H.A. Day CERN, Geneva, Switzerland A. Faus-Golfe LAL, Orsay, France F. Toral CIEMAT, Madrid, Spain
	A first stripline kicker prototype for beam extraction from the CLIC Damping Rings (DRs) has been designed at IFIC and CIEMAT, with excellent field homogeneity, good power transmission and low beam coupling impedance. The prototype has been built by the company Trinos Va\-cuum Projects, and laboratory tests and measurements have been carried out at CERN to characterize, without beam, the electromagnetic response of the striplines. In this paper, we present the measurements of the transverse beam coupling impedance, using the coaxial wire method, and a comparison with simulations. Furthermore, results of DC breakdown tests, using High Vol\-ta\-ge (HV) power supplies, are also reported.
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WEPMN070	Measurement Techniques and Application of Combined Parallel/Orthogonal Magnetic Bias on a Ferrite Tuned Resonator in Low Frequency Range (3-10 MHz)	cavity, solenoid, power-supply, network	3087
	G. Favia, F. Caspers, M. Morvillo, C. Rossi, C. Vollinger CERN, Geneva, Switzerland
	We present several measurement methods for evaluation of magnetic properties of magnetically biased and non-biased ferrite samples in a coaxial test fixture. One important aspect is the crosscheck of results obtained by using different and independent measurement and evaluation methods. Since a rather high DC bias current has to be applied, a dedicated network was designed that allows the passage of up to 50 A DC without degradation of the RF performance. With a combination of calibration methods and a compensating topology with two identical sample holders, a good performance was achieved. In this context, magnetic material parameters for about 10 different types of ferrite were obtained. The orthogonal magnetic bias was added by placing the entire test fixture into a large toroidal coil. Thus, the bias field can be supplied independently from, and in addition to the classical parallel bias. An optimal combination between the two biasing fields was found, resulting in a reduction of magnetic losses up to 50% on certain ferrites. We show that the mixed magnetization, normally used for garnets only, is beneficial also for other types of ferrites.
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WEPHA002	Electromagnetic Characterization of NEG Properties Above 200 GHz for the CLIC Damping Rings	simulation, damping, network, electron	3097
	E. Koukovini-Platia, G. Iadarola, G. Rumolo, C. Zannini CERN, Geneva, Switzerland
	Non-Evaporable Getter (NEG) will be used in the CLIC electron damping rings (EDR) to suppress fast beam ion instabilities due to its effective pumping ability. The electromagnetic (EM) characterization of the NEG properties up to high frequencies is required for the correct impedance modeling of the DR components. The properties are determined using WR-3.4 and WR-1.5 rectangular waveguides, based on a combination of experimental measurements of the complex transmission coefficient S21 with a Vector Network Analyzer (VNA) and CST 3D EM simulations, for the frequency range of 220-330 GHz and 500-750 GHz. The results obtained using NEG-coated Aluminum (Al) waveguides are presented in this paper.
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WEPHA005	Characterization of the RF Fingers Contact Force for the LHC Warm Vacuum Bellow Modules	vacuum, alignment, operation	3106
	C. Blanch Gutiérrez, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan CERN, Geneva, Switzerland
	Along the 27 Km of LHC beam pipe, various types of vacuum bellow modules are needed to compensate the mechanical misalignments of the vacuum chambers during installation and to absorb their thermal expansion during the bake-out. In order to reduce the beam impedance during operation with beams these modules are equipped with RF bridges to carry the image current. They are usually made out of a copper tube insert at one side and Cu-Be RF fingers at the other end of the module. A spring is used to keep the contact between the RF fingers and the tube insert. The geometry and the choice of this spring become critical to ensure a good electrical contact. In this paper, a description of the test bench used to measure the contact force together with the procedure applied and the measurements performed are given. A summary of the maximum radial and axial offsets between the RF fingers and the insert tube while keeping a good electrical contact is presented.
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WEPHA025	Design of a Variable X-band RF Power Splitter	network, polarization, operation, scattering	3167
	H. Zha, A. Grudiev, D. Gudkov, I. Syratchev CERN, Geneva, Switzerland
	The design of a two output ports, high power X-Band RF splitter with arbitrary split ratio is presented. This ratio is adjusted by mechanical changing the position a special RF short circuit piston. The piston is mounted on a step-motor providing the precise movement. Special measures were taken in the design to decrease the maximum electrical field on the cooper surface, as well as to maximise the bandwidth of the device. This splitter will be tested in the high power X-band test stand at CERN.
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WEPTY014	Development of Fast Kickers for the APS MBA Upgrade	kicker, simulation, high-voltage, injection	3286
	C. Yao, J. Carwardine, A.R. Cours, F. Lenkszus, R.R. Lindberg, L.H. Morrison, X. Sun, J. Wang, F. Westferro, A. Xiao ANL, Argonne, Illinois, USA
	Funding: *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357. The APS multi-bend achromat (MBA) upgrade storage ring will support two bunch fill patterns: a 48-singlets and a 324-singlets. A “swap out” injection scheme is adopted. In order to minimize the beam loss and residual oscillation of injected beam and to minimize the perturbation of stored beam during a swap-on injection, the rise, fall, and flat-top parts of the kicker pulse must be held within a 22.8-ns interval. Traditional ferrite-core-type kickers can’t meet the timing requirements; therefore, we decided to use stripline-type kickers. We have completed a preliminary design of a prototype kicker geometry. Procurement of the pulser supply and other components of an evaluation system is under way. We report the specification and design of the fast kicker and current status.
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WEPTY016	RF Modeling of a Helical Kicker for Fast Chopping	kicker, simulation, experiment, linac	3293
	M.H. Awida, A.Z. Chen, T.N. Khabiboulline, G.W. Saewert, V.P. Yakovlev Fermilab, Batavia, Illinois, USA
	High intensity proton particle accelerators that supports several simultaneous physics experiments requires sharing the beam. A bunch by bunch beam chopper system located after the Radio Frequency Quadrupole (RFQ) is required in this case to structure the beam in the proper bunch format required by the several experiments. The unused beam will need to be kicked out of the beam path and is disposed in a beam dumb. In this paper, we report on the RF modeling results of a proposed helical kicker. Two beam kickers constitutes the proposed chopper. The beam sequence is formed by kicking in or out the beam bunches from the streamline. The chopper was developed for Project X Injection Experiment (PXIE).
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WEPTY027	Kicker Pulsers for Recycler Nova Upgrades	cathode, kicker, high-voltage, controls	3324
	C.C. Jensen Fermilab, Batavia, Illinois, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. An upgrade of the Recycler injection kicker system required a faster rise time pulser. This system required a field rise and fall time of < 57 ns and a field flattop of 1.6 μs. This paper describes the variety of improvements made over the years that have resulted in this latest thyratron pulser. The effects of the trigger, the reservoir and the load impedance on delay and rise time will be discussed.
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WEPTY044	Phase Transients in the Higher-Harmonic RF Systems For the ALS-U Proposal	simulation, experiment, beam-loading, synchrotron	3372
	J.M. Byrd, S. De Santis, T.H. Luo, C. Steier LBNL, Berkeley, California, USA
	Funding: This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231. The ALS upgrade proposal (ALS-U) requires lengthening the bunch by a factor of at least four in order to increase the beam lifetime to acceptable values. Due to the presence of gaps in the fill pattern, required by the injection/extraction kicker system, the beam-induced voltage in the passive, normal-conducting, cavities which we plan to use is not constant over the length of a bunch train. We present our result on the optimal tuning of the harmonic cavities to obtain the best lifetime increase, including the effects of strongly non-gaussian bunch shapes and wakefield distortions of the potential well.
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WEPTY051	Stripline Kicker for Integrable Optics Test Accelerator	kicker, proton, electron, operation	3390
	S. A. Antipov University of Chicago, Chicago, Illinois, USA A. Didenko, V.A. Lebedev, A. Valishev Fermilab, Batavia, Illinois, USA
	Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy. We present a design of a stripline kicker for Integrable Optics Test Accelerator (IOTA). For its experimental program IOTA needs two full-aperture kickers, capable to create an arbitrary controllable kick in 2D. For that reason their strengths are variable in a wide range of amplitudes up to 16 mrad, and the pulse length 100 ns is less than a revolution period for electrons. In addition, the kicker has a physical aperture of 40 mm for a proposed operation with proton beam, and an outer size of 70 mm to fit inside existing quadrupole magnets to save space in the ring. Computer simulations using CST Microwave Studio show high field uniformity and wave impedance close to 50 Ω.
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WEPTY056	Novel High Power Sources for the Physics of Ionospheric Modification	gun, cathode, simulation, electron	3398
	B. Beaudoin, T.M. Antonsen, I. Haber, T.W. Koeth, A.H. Narayan, G.S. Nusinovich, K.J. Ruisard UMD, College Park, Maryland, USA J. Rodgers Naval Research Laboratory (NRL), Washington, USA
	Funding: This work is supported by the Air Force Office of Scientific Research under grant FA95501410019. The ionosphere plays a controlling role in the performance of critical civilian and DoD systems including the ELF-ULF communications. The objective of Ionospheric Modification is to control triggered processes to improve the performance of trans-ionospheric C3I systems and develop new applications that take advantage of the ionosphere as an active plasma medium. A key instrument is the Ionospheric Heater, a powerful HF transmitter that modifies the properties of the ionospheric plasma by modulating the electron temperature at preselected altitudes. A major reason for the development of a mobile source is that it would allow investigators to conduct the needed research at different latitudes without building permanent installations. As part of a MURI, UMD will develop a powerful RF source utilizing IOT technology in class-D amplifier mode. This technology was chosen because it has the potential to operate at very high efficiency. Some of the technical challenges presented in this paper will include a gun design that minimizes intercepted current, a compact tunable cavity, an efficient modulator system capable of modulating a high power beam and output couplers to feed the antennas.
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WEPTY063	Co-Linear X-Band Energy Booster (XCEB) Cavity and RF System Details	cavity, electron, extraction, linac	3421
	T. Sipahi, S. Biedron, S.V. Milton CSU, Fort Collins, Colorado, USA
	Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers. At the Colorado State University Accelerator Laboratory (CSUAL) we would like to adapt this technology to our 1.3-GHz, L-band accelerator system in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the design details of the X-band structures that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structure while driven solely by the beam from the L-band system.
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WEPTY071	Time Resolved Cryogenic Cooling Analysis of the Cornell Injector Cryomodule	HOM, simulation, cryogenics, operation	3443
	R.G. Eichhorn, S.R. Markham, P. Quigley, E.N. Smith Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Managing parallel cryogenic flows has become a key challenge in designing efficient and smart cryo-modules for particle accelerators. In analyzing the heating dynamics of the cornell high current injector module a power-full computational tool has been set-up allowing time resolved analysis and optimization. We will describe the computational methods and data sets we have used, report the results and compare them to measured data from the module being in good agreement. Mitigation strategies developed on basis of this model have helped pushing the operational limitations.
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WEPTY083	Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype	HOM, cavity, factory, damping	3475
	S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov LANL, Los Alamos, New Mexico, USA C.H. Boulware, T.L. Grimm, A. Rogacki Niowave, Inc., Lansing, Michigan, USA
	We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.
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WEPWI030	Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design	cavity, cryomodule, HOM, dipole	3551
	H. Wang, G. Cheng, W.A. Clemens, G.K. Davis, K. Macha, R.B. Overton, D. Spell JLab, Newport News, Virginia, USA
	Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177. After the electromagnetic design * and the mechanical design ** of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported. * H. Wang, etc., Proceeding of IPAC2013, Shanghai, China, WEPWO073. ** G. Cheng, etc., Proceeding of PAC2013, Pasadena, CA, WEPAC47.
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WEPWI037	Imperfection and Tolerance Analysis of HOM Couplers for ODU/SLAC 400 MHz Crabbing Cavity	HOM, cavity, dipole, luminosity	3572
	S.U. De Silva, J.R. Delayen, H. Park ODU, Norfolk, Virginia, USA Z. Li SLAC, Menlo Park, California, USA R.G. Olave Old Dominion University, Norfolk, Virginia, USA
	In preparation for the LHC High Luminosity upgrade, a 400 MHz crab cavity has been developed jointly at ODU/SLAC, including two higher order mode couplers designed to dampen the wakefields in order to comply with the impedance budget specified for the LHC system. During fabrication, assembly, and processing of the couplers, a number of imperfections may arise that could modify the higher order mode spectrum and the associated impedance for each mode. We present here a detailed study of the imperfections of the horizontal- and vertical- HOM couplers, and the associated allowed tolerances for manufacture, assembly and processing.
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WEPWI054	Design and Test of the RHIC CMD10 Abort Kicker	kicker, vacuum, network, coupling	3612
	H. Hahn, M. Blaskiewicz, K.A. Drees, W. Fischer, W. Meng, J.-L. Mi, C. Montag, C. Pai, J. Sandberg, N. Tsoupas, J.E. Tuozzolo, W. Zhang BNL, Upton, Long Island, New York, USA
	Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy. Planned and unplanned thyratron pre-fire triggered beam dumps have been observed in the yellow ring that were associated with quenches of the superconducting main ring magnets as the proton intensities increased in the FY10¹³ run. The increasing vacuum level indicated beam induced kicker ferrite heating causing lower magnetic kick field at a nominal pulse current. In anticipation of higher current and shorter bunches in FY2015 an accelerator improvement program was initiated to reduce the longitudinal coupling impedance with changes to the eddy-current strip geometry using Opera simulations and to change the CMD5005 to CMD10 ferrite. Results of the standard impedance measurements and of pulse current in heating tests to 170 °C are reported. All 10 dump kickers are being modified and are encapsulated with a cooling system for installation in the rings.
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WEPWI059	Higher Order Mode Filter Design for Double Quarter Wave Crab Cavity for the LHC High Luminosity Upgrade	HOM, cavity, luminosity, coupling	3627
	B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, S. Verdú-Andrés, Q. Wu BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA G. Burt, B.D.S. Hall Cockcroft Institute, Lancaster University, Lancaster, United Kingdom G. Burt Lancaster University, Lancaster, United Kingdom R. Calaga, O. Capatina CERN, Geneva, Switzerland T.J. Jones STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom
	Funding: Work partly supported by US LARP, by US DOE under contract No. DE-AC02-05CH11231 and through BSA under contract No. DE-AC02-98CH10886. Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404. A double quarter wave crab cavity (DQWCC) was designed for the Large Hadron Collider (LHC) luminosity upgrade. A compact Higher Order Mode (HOM) filter with wide stop band at the deflecting mode is developed for this cavity. Multi-physics finite element simulation results are presented. The integration of this design to the cavity cryomodule is described.
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WEPWI061	Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac	cavity, resonance, electron, simulation	3634
	B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, K.S. Smith, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman BNL, Upton, Long Island, New York, USA S.A. Belomestnykh, I. Ben-Zvi Stony Brook University, Stony Brook, USA V. Veshcherevich Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA
	Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE. To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for bunch stretching and energy spread correction. In this paper we report the design of these two cavities.
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THPF027	Ten Gap Model of a New Alvarez DTL Cavity at GSI	simulation, cavity, ion, DTL	3748
	A. Seibel, O.K. Kester IAP, Frankfurt am Main, Germany X. Du, L. Groening, S. Mickat GSI, Darmstadt, Germany
	In order to meet the challenges of the FAIR project at GSI requiring highest beam intensities an upgrade of the existing Universal Linear Accelerator (UNILAC) is planned. The 10⁸ MHz cavities will be replaced by new rf-structures of the same frequency. Simulations are done to improve the rf-properties. The geometry of the drift tubes is to be changed to a smoother curvature to reach a homogeneous surface field distribution and higher shunt impedances. To check the necessity of cooling channels, simulations on the temperature distribution at the drift tubes and stems are conducted. A test bench for low power rf-measurements with a 10 gap aluminum model (scale 1:3) is under construction. The modular mechanical design of the model will allow probing experimentally a wide range of drift tube and stem geometries. With the bead pull method the electrical field distribution will be measured as well as the field stability with respect to parasitic modes. Additionally, appropriate locations along the cavity to place fixed and dynamic rf-frequency tuners will be determined.
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THPF034	Injection Kicker for HESR at FAIR using Semi-Conductor Switches	injection, kicker, vacuum, antiproton	3770
	R. Tölle, N. Bongers, F.M. Esser, R. Gebel, S. Hamzic, H. Jagdfeld, F. Klehr, B. Laatsch, L. Reifferscheidt, M. Retzlaff, L. Semke, H. Soltner, H. Stockhorst FZJ, Jülich, Germany S. Antoine, W. Beeckman, P. Bocher, O. Cosson, P. Jivkov, D. Ramauge Sigmaphi, Vannes, France
	The High Energy Storage Ring for Antiprotons is going to be built at FAIR in Darmstadt on the extended GSI campus. It will receive the antiprotons via the Collector Ring (CR). Using a barrier bucket, the circulating particles will be compressed into one half of the circumference. New particles have to be injected into the remaining half. Thus rise and fall time must not exceed 220 ns each with a flat top of 500 ns. A kick angle of 6.4 mrad is required at 13 Tm magnetic rigidity. The system must allow pole reversal for injection of positively charged particles. With a voltage lower than 40 kV a semi-conductor based pulser is going to be realized. Boundary conditions and the status of preparatory work are described. Simulation results and available measurements are presented.
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THPF049	The Simulation and Manufacture of the Room Temperature Cross-bar H Type Drift Tube Linac	cavity, DTL, proton, rfq	3811
	J.H. Li China Institute of Atomic Energy, Beijing, People's Republic of China Z. Li SCU, Chengdu, People's Republic of China
	Funding: This work is supported by the National Natural Science Foundation of China (NSFC). The room temperature Cross-bar H Type Drift Tube Linac (CH-DTL) is one of the candidate acceleration structures working in CW mode. In order to optimize the parameters, the 3 dimensional electromagnetic field of the CH-DTL cavity is simulated. The method of parameter sweeping with constraint variable is better than the method of parameter sweeping with only one variable during the optimization. In order to simplify the manufacture, the drift tube surface can be designed as spherical shape. The effective shunt impedance of the CH-DTL cavity with cylinder end cup is better than that with cone cup.
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Paper

Title

Other Keywords

Page

MOAD1

Development of High Gradient RF System for J-PARC Upgrade

cavity, operation, proton, acceleration

50

C. Ohmori, K. Hara, K. Hasegawa, M. Toda, M. Yoshii
KEK, Ibaraki, Japan
M. Nomura, T. Shimada, F. Tamura, M. Yamamoto
JAEA/J-PARC, Tokai-mura, Japan
A. Schnase
GSI, Darmstadt, Germany

A new 5-cell cavity has been developed for the upgrade of the J-PARC Main Ring. In the cavity, high impedance magnetic alloy - Finemet FT3L, cores are loaded. The cavity was installed and has been used for the 250 kW beam operation. The cavity is operated with the RF voltage of 70 kV which is two times higher voltage than the present cavities. Eight more cavities will be assembled and installed in the next two years to increase the repetition rate of the Main Ring. This paper describes status of cavity operation under the beam loading and status of the mass productions of the cavities.

Slides MOAD1 [2.551 MB]

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MOBD1

Preliminary Design of the High-Luminosity LHC Beam Screen with Shielding

vacuum, shielding, luminosity, cryogenics

60

C. Garion, V. Baglin, R. Kersevan
CERN, Geneva, Switzerland

A new beam screen is needed in the High-Luminosity LHC (HL-LHC) final focusing magnets. Such an essential vacuum component, while operating in the range 40-60 K, has to ensure the vacuum performance and to prevent the beam-induced heating from reaching the cold bore which is at 1.9 K. In addition, they have to shield the cold mass from physics debris coming from the nearby beam collision points. To such purpose, energy absorbers made of tungsten alloy are installed onto the beam screen in the vacuum system. In this contribution, the proposed mechanical design is shown; it covers different thermomechanical aspects such as the behaviour during a magnet quench and the heat transfer from the tungsten absorbers to the cooling tubes. Assembly and manufacturing tolerances are also considered to evaluate the impact on the aperture. Results obtained with a short prototype assembly test are discussed.

Slides MOBD1 [3.089 MB]

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MOBD3

Development of a 9 MHz 15 kW Solid-state CW Amplifier for RHIC

network, cavity, resonance, feedback

67

S.C. Dillon
Tomco Technologies, Stepney, South Australia, Australia

This paper describes the technical details of the development of a high-power solid-state amplifier for Brookhaven Laboratory. The amplifier must withstand short duration events of 100% full-power reflection, and also must guarantee delivery of continuous power into any load impedance at any angle.

Slides MOBD3 [10.800 MB]

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MOPWA001

Instability Thresholds and Tune Shift Estimation for Sirius

feedback, emittance, damping, simulation

70

F.H. de Sá, L. Liu, N. Milas, X.R. Resende
LNLS, Campinas, Brazil

In this work we present the evaluation of longitudinal and transverse instability thresholds as well as tune shifts for Sirius using time and frequency domain codes that are being developed in-house and take into account various effects on the beam instability, such as bunch by bunch feedback system, quadrupolar impedances from undulator chambers and tune spreads.

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MOPWA018

Loss Factor and Impedance Analysis of Warm Components of BERLinPro

factory, simulation, operation, wakefield

128

H.-W. Glock, M. Abo-Bakr, J. Kolbe, F. Pflocksch, A. Schälicke
HZB, Berlin, Germany
H.-W. Glock, C. Potratz
COMPAEC e.G., Rostock, Germany

Funding: Work supported by German Bundesministerium für Bildung und Forschung, Land Berlin, and grants of Helmholtz Association
The ongoing component design for the HZB 50 MeV, 100mA ERL project BERLinPro is accompanied by loss factor and impedance computations. A list of accelerator components including bellows, collimators, tapers, shutter valves etc. is given, some of them with alternative shapes. Loss factors, calculated using CSTParticleStudio®, are presented together with important properties of the impedance spectrum. Scaling of the loss factors with respect to bunch length is calculated on base of the numerical simulations and is used to extrapolate down to a bunch length (1 standard deviation) of 0.6 mm, which is hard to reach directly in numerical simulations.

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MOPWA020

Longitudinal Stability Of Short Bunches in Storage Rings with Strong Longitudinal Focusing

synchrotron, dipole, simulation, resonance

135

P. Kuske
HZB, Berlin, Germany

Funding: work supported by the BMBF
In the BESSY VSR project, the variable bunch length storage ring, two high gradient accelerating structures at 1.5 and 1.75 GHz will be phased such that long and short bunches can be stored simultaneously. The longitudinal stability of the short bunches is investigated taking into account the shielded CSR- and a purely inductive impedance. Multi particle tracking studies and numerical solutions of the Vlasov-Fokker-Planck equation show that threshold currents for short bunches do not follow the simple scaling law which was found for long bunches. The inductive impedance can even lower the thresholds for the instability. With an 80 times increased accelerating gradient and reasonable assumptions on the inductive impedance for shorter bunches stable operation can be expected with bunches 1.8 ps long (RMS-value) and 0.8 mA current. According to the calculations and operating in a dedicated low-α mode will produce stable 40 μA bunches with 400 fs length

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MOPWA024

Estimation of the Ion Density in Accelerators using the Beam Transfer Function Technique

ion, electron, betatron, synchrotron

147

D. Sauerland, W. Hillert
ELSA, Bonn, Germany
A. Meseck
HZB, Berlin, Germany

Funding: Funded by the federal ministry of education and science of Germany
The ELSA stretcher ring of Bonn University serves external hadron physics experiments with a quasi continuous electron beam of up to 3.2 GeV energy. Ions, being generated by collisions of the circulating electrons with the residual gas molecules, accumulate inside the beam potential, causing incoherent tune shifts and coherent beam instabilities. Detailed measurements were carried out in which ion dynamics is studied in dependence of beam energy and current, filling patterns and bias voltages of the ion clearing electrodes. By measuring the beam transfer function using a broadband transversal kicker, we were able to derive an estimate of the average ion density from the shift and broadening of the tune peak. In this contribution first results of these measurements are presented.

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MOPWA031

A New Approach for Resistive Wakefield Calculations in Time Domain

wakefield, simulation, cavity, controls

168

A.V. Tsakanian, H. De Gersem, E. Gjonaj, T. Weiland
TEMF, TU Darmstadt, Darmstadt, Germany
M. Dohlus, I. Zagorodnov
DESY, Hamburg, Germany

We report on a new numerical technique for the computation of the wakefields excited by ultra-short bunches in the structures with walls of finite conductivity. The developed 3D numerical method is fully time domain. It is based on special Staggered Finite Volume Time Domain (SFVTD) method and has no numerical dispersion in all three axial directions simultaneously. This results in large saving in computational time as well as improved accuracy. The resistive boundary model applies Surface Impedance Boundary Condition (SIBC) evaluation in time domain and covers boundary effects like frequency dependent conductivity, surface roughness and metal oxidation. A good agreement between numerical simulation and perturbation theory is obtained. In addition the new method allows implementation of moving mesh approach that considerably reduces requirements on computational resources. The developed method is especially effective for short range resistive wakefield calculations excited by ultra-short bunches used in FEL based LINACs.

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MOPWA058

Measurement Results of the Impedance of the RF-cavity at the RCS in J-PARC

cavity, injection, kicker, proton

255

Y. Shobuda, H. Harada, H. Hotchi
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

The kicker impedance dominates at the RCS in J-PARC. Recently, we observe beam instabilities, which are not explained by the kicker. As a candidate causing the beam instability, the impedance of the RF-cavity is measured. The longitudinal impedance is measured by stretching a single-wire inside the cavity. On the other hand, the measurement of the transverse impedance is done by horizontally shifting the single-wire, due to the accuracy problem. The measured impedance is too low to explain the beam instability.

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MOPWA060

THE COUPLING IMPEDANCE MEASUREMENT OF THE FAST EXTRACTION KICKER IN CSNS/RCS *

kicker, coupling, extraction, proton

262

L. Huang, Y.D. Liu, S. Wang
IHEP, Beijing, People's Republic of China

Rapid Cycling Synchrotron of the China Spallation Neutron Source is a high intensity proton accelerator. In order to high intensity beam operation, the beam coupling impedance of the extracted kickers must be controlled. The measurement of longitudinal and transverse coupling impedance of the extraction kicker is described.
Supported by National Natural Science Foundation of China (11175193, 11275221)

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MOPJE026

Revision of the Impedance Model for the Interpretation of the Single Bunch Measurements at ALBA

vacuum, undulator, simulation, storage-ring

330

T.F.G. Günzel, U. Iriso
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain

Recent measurements showed that the ALBA transverse impedance model was able to explain 65% of the measured single bunch vertical detuning. * This report shows the revision of the impedance model developed to match latest single bunch measurements performed to evaluate the total effective machine impedance and impedance of specific elements, like in-vacuum undulators or a recently installed pinger magnet. The model improvement includes a better bunch length parameterisation, re-calculation of several vacuum chamber elements with Gdfidl, and inclusion of elements neglected so far in the impedance budget. We also show and discuss the computation of the resistive wall impedance using ImpedanceWake2D.
* T.Günzel, U.Iriso, F.Perez, E.Koukovini-Platia, G.Rumolo, "Analysis of the single bunch measurements at the ALBA Storage Ring", TUPRI052, proc. of IPAC14 (2014).

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MOPJE027

Beam-based Impedance Characterization of the ALBA Pinger Magnet

simulation, vacuum, injection, synchrotron

334

U. Iriso, T.F.G. Günzel
ALBA-CELLS Synchrotron, Cerdanyola del Vallès, Spain
H. Bartosik, E. Koukovini-Platia, G. Rumolo
CERN, Geneva, Switzerland

The ALBA pinger magnet consists on two short kickers (for horizontal and vertical planes) installed in a single Titanium coated ceramic vacuum chamber. Single bunch measurements in the vertical plane were performed in the ALBA Synchrotron Light Source before and after the pinger installation, and by comparing the Transverse Mode Coupling Instability (TMCI) thresholds for zero chromaticity, we infer the pinger impedance and compare it with the model predictions. We also perform measurements for negative chromaticities and results are reported in this paper.

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MOPJE035

An Extended SPS Longitudinal Impedance Model

vacuum, kicker, simulation, resonance

360

J.V. Campelo, T. Argyropoulos, T. Bohl, F. Caspers, J. F. Esteban Müller, J.B. Ghini, A. Lasheen, D. Quartullo, B. Salvant, E.N. Shaposhnikova, C. Zannini
CERN, Geneva, Switzerland

Longitudinal multi-bunch instability in the CERN SPS with a very low intensity threshold is a serious limitation for the future doubling of bunch intensity required by Hi-Lumi LHC project. A complete and accurate impedance model is essential to understand the nature of this instability and to plan possible cures. This contribution describes in detail the current longitudinal impedance model of the SPS. Recently, the model was updated with new findings and includes now the impedance of accelerating cavities, kicker and septum magnets, beam position monitors, vacuum Flanges, shielded and unshielded pumping ports, electrostatic septa and resistive wall. Electromagnetic simulations and bench measurements were used to build the model. The contribution from each element is described and compared to the total machine impedance. Together with relevant beam measurements and simulations, the analysis of the different sources of impedance is used to identify the source of the longitudinal instability limiting the SPS performance so that the responsible elements can be acted upon.

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MOPJE036

Longitudinal Impedance Characterization of the CERN SPS Vacuum Flanges

resonance, vacuum, simulation, damping

363

J.V. Campelo
CERN, Geneva, Switzerland

This contribution describes the thorough studies carried out to characterize the longitudinal impedance of the CERN SPS vacuum flanges, which are believed to be the main source of LHC beam instability. Around 500 high-impedance flanges of 8 different types have been identified. Three factors play an important role in the characterization of these flanges: the type of vacuum chambers that the flange interconnects, whether or not both sides are electrically isolated (by means of an enamel coating) and, finally, the presence of damping resistors which damp high-Q resonances. Not only, full-wave electromagnetic field simulations, but also RF measurements have been used to evaluate the impedance of these elements. The R/Q of the relevant resonances was measured using the well-known bead-pull technique. In particular, a subset of around 150 flanges has been found to be the source of a high-impedance resonance at 1.4 GHz, also observed in beam measurements. Guidelines on how to reduce the impedance of these elements are also presented.

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MOPJE038

Impedance Studies of the LHC Injection Kicker Magnets for HL-LHC

coupling, kicker, injection, simulation

370

H.A. Day, M.J. Barnes, L.M.C. Feliciano
CERN, Geneva, Switzerland

The LHC injection kicker magnets (MKIs) experienced strong heating during the first operational run, identified as being caused by power loss due to wakefields induced by stored beam. Studies of the beam coupling impedance of the beam screen, a series of conductors embedded in a ceramic tube placed in the ferrite yoke to screen the ferrite from the beam, resulted in new design offering improved screening: this is predicted to reduce the heating to acceptable levels for operation with 25ns beam during Run 2 of the LHC. However higher beam intensities proposed for HL-LHC operation are predicted to again cause strong heating to occur. Further studies have been carried out to reduce the beam induced power loss by optimising the beam screen design, some key results and findings of which are presented here.

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MOPJE047

Chromaticity Dependence of the Transverse Effective Impedance in the CERN Proton Synchrotron

proton, synchrotron, controls, space-charge

395

S. Persichelli, N. Biancacci, S.S. Gilardoni, A. Huschauer, E. Métral, B. Salvant, R. Wasef
CERN, Geneva, Switzerland
M. Migliorati
University of Rome La Sapienza, Rome, Italy

The current knowledge of the transverse impedance of the Proton Synchrotron (PS) has been established with beam-based measurements at different energies. The transverse coherent tune shift as a function of the beam intensity has been measured in order to evaluate the total effective imaginary part of the transverse impedance and its localization in the accelerator at the energies of 2, 7, 13 and 25 GeV. Measurements have been performed changing the chromaticity for every tune shift scan with intensity. The data analysis revealed an increase of impedance with chromaticity for all the energies considered. That transverse impedance can be compared with the previously evaluated theoretical impedance budget taking into account the individual contribution of several machine devices. The missing impedance is finally highlighted.

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MOPJE049

Benchmarking the CERN-SPS Transverse Impedance Model with Measured Headtail Growth Rates

simulation, kicker, optics, vacuum

402

C. Zannini, H. Bartosik, G. Iadarola, G. Rumolo, B. Salvant
CERN, Geneva, Switzerland

The latest SPS transverse impedance model includes kicker magnets, wall impedance, transition pieces (e.g. flanges and vacuum chamber discontinuities), beam position monitors and RF cavities. The model has already been successfully benchmarked against coherent tune shift and transverse mode coupling instability measurements. In this paper we present measurements of the headtail growth rates for a wide range of negative chromaticities and for two different configurations of machine optics (nominal and low gamma transition). The measurement results are compared with HEADTAIL simulations using the wake fields obtained from the SPS transverse impedance model.

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MOPJE050

Transverse Impedance Model of the CERN-PSB

space-charge, kicker, simulation, vacuum

406

C. Zannini, G. Iadarola, K.S.B. Li, T.L. Rijoff, G. Rumolo
CERN, Geneva, Switzerland
B. Jones
STFC/RAL/ISIS, Chilton, Didcot, Oxon, United Kingdom
T.L. Rijoff
TU Darmstadt, Darmstadt, Germany

In the framework of the PS-Booster upgrade project an accurate impedance model is needed in order to determine the effect on the beam stability and assess the impact of the new devices before installation in the machine. This paper describes the PSB impedance model which includes resistive wall, indirect space charge, flanges, step transitions, ejection kicker including cables, injection kickers and cavities. Each impedance contribution has been computed for different energies in the PSB cycle. Measurements of the coherent tune shifts have been performed and compared to calculations based on the impedance model.

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MOPJE064

Beam Impedance Optimization of the TOTEM Roman Pots

detector, simulation, cavity, vacuum

452

N. Minafra
CERN, Geneva, Switzerland

The TOTEM experiment has been designed to measure the total proton-proton cross section and to study elastic and diffractive scattering at the LHC energy. The measurement requires detecting protons at distances as small as 1 mm from the beam center: TOTEM uses Roman Pots (RP), special beam pipe insertions, to move silicon detectors close to the beams to detect particles very near the beam axis. In the first period of running of the LHC no problems were detected with retracted Roman Pots and during insertions in special runs; however, during close insertions to highest intensity beam, impedance heating has been observed. After the LS1 the LHC beam current will increase and the equipment that can interact with the beam needed to be optimized. A new RP, optimized to minimize the beam coupling, has been designed with the help of CST Particle Studio; a prototype has been used to test the simulation results in the laboratory with wire and probe measurements. Furthermore, in both the old and the new RPs, new ferrites have been installed. The new ferrite material has a higher Curie temperature than the one used before LS1 and a thermal treatment at 1000°C has been applied to reduce the out-gassing.

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MOPJE072

Simulations and Measurements of Longitudinal Coupled-bunch Instabilities in the CERN PS

feedback, cavity, synchrotron, luminosity

479

L. Ventura, H. Damerau, M. Migliorati, G. Sterbini
CERN, Geneva, Switzerland
M. Migliorati, L. Ventura
INFN-Roma1, Rome, Italy
M. Migliorati
University of Rome La Sapienza, Rome, Italy
L. Ventura
University of Rome "La Sapienza", Rome, Italy

Among various and challenging objectives of the LHC Injectors Upgrade project (LIU), one aim is to double the beam intensity of the CERN Proton Synchrotron (PS) in order to achieve the integrated luminosity target of the High-Luminosity LHC project (HL-LHC). A known limitation to reach the required high intensity is caused by the longitudinal coupled-bunch oscillations developing above the transition energy. The unwanted oscillations induce large bunch-to-bunch intensity variations not compatible with the specifications of the future LHC-type beams. A wide-band longitudinal damper has been installed in the PS to suppress these instabilities and is going to be commissioned. A measurement campaign of coupled-bunch oscillations has been launched to substantiate the extrapolations and predictions for the future High Luminosity LHC beam with the final aim to determine the maximum intensity that could be provided to the LHC. In parallel a Simulink© model of the PS is going to be implemented to predict the machine behavior in the parameter space of LIU and to be used during the beam commissioning and optimization of the feedback system.

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MOPMA001

Comparison of Measurements and Simulations for Single Bunch Instabilities at Diamond

wakefield, radiation, simulation, synchrotron

521

M. Atay, R. Bartolini
JAI, Oxford, United Kingdom
R. Bartolini, R.T. Fielder, I.P.S. Martin
DLS, Oxfordshire, United Kingdom

The single bunch dynamics in the Diamond storage ring has been analysed with a multiparticle tracking code and compared with the results of a wealth of diagnostics, including streak camera, Schottky diodes and FTIR spectra. The interplay of various wakefield sources has been studied and it has been found that the THz spectrum can be reproduced in many cases with simple impedance models, both below and above the bursting threshold.

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MOPMA006

Modeling RF Feedback in Elegant for Bunch-Lengthening Studies for the Advanced Photon Source Upgrade

feedback, cavity, injection, storage-ring

540

T.G. Berenc, M. Borland
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice includes a passive bunch-lengthening cavity to alleviate lifetime and emittance concerns. Feedback in the main radio-frequency (rf) system affects the overall impedance presented to the beam in this double rf system. To aid beam stability studies, a realistic model of rf feedback has been developed and implemented in elegant and Pelegant.

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MOPMA007

Tracking Studies of a Higher-Harmonic Bunch-Lengthening Cavity for the Advanced Photon Source Upgrade

simulation, cavity, feedback, timing

543

M. Borland, T.G. Berenc, R.R. Lindberg, A. Xiao
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
The Advanced Photon Source (APS) multi-bend achromat (MBA) lattice will require a bunch-lengthening cavity to decrease the effects of Touschek scattering on the beam lifetime and of intrabeam scattering on the beam emittance. Using ELEGANT, we've performed tracking studies of a passive, i.e. beam-driven, fourth-harmonic cavity in the MBA lattice, including the predicted longitudinal impedance of the ring. The studies include an exploration of the required detuning and loaded Q of the main rf cavities and the harmonic cavity in order to stabilize the beam and achieve significant lengthening. We also studied the effects of bunch population variation and missing bunches. The computed bunch profiles are used for computation of the Touschek lifetime, verifying the beneficial effects in detail.

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MOPMA009

Improvements in Modeling of Collective Effects in ELEGANT

simulation, cavity, collective-effects, lattice

549

M. Borland, R.R. Lindberg, A. Xiao
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
ELEGANT has long had the ability to model collective effects in various ways, including beam-driven cavity modes, short-range wakes, and coherent synchrotron radiation. Recently, we made improvements specifically targeting simulations that require multiple bunches in storage rings. The ability to simulate long-range, non-resonant wakes was added, which can be used for example to study the effect of the resistive wall wake and multibunch instabilities. We also improved the implementation of short-range and resonant wakes to make them more efficient for multibunch simulations. Finally, improvements in the parallel efficiency were made that allow taking advantage of larger parallel resources.

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MOPMA025

CSR Induced Microbunching Gain Estimation including Transient Effects in Transport and Recirculation Arcs

dipole, lattice, simulation, damping

596

C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA
D. Douglas, R. Li, C. Tennant
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
The coherent synchrotron radiation (CSR) of a high brightness electron beam traversing a series of dipoles, such as transport or recirculation arcs, may result in the microbunching instability (μBI). To accurately quantify the direct consequence of this effect, we further extend our previously developed semi-analytical simulation [C. -Y. Tsai et al., FEL Conference 2014 (THP022)] to include more relevant coherent radiation models than the steady-state free-space CSR impedance, such as the entrance and exit transient effects, which derive from upstream beam entering to and exiting from individual dipoles and propagating across the elements to downstream straight sections. Then we semi-analytically solve the linearized Vlasov equation for the amplification factor. The resultant gain functions and spectra for our example lattices are presented and compared with particle tracking simulation. Some underlying physics with inclusion of these effects are also discussed.

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MOPMA040

Analysis of Beam Transverse Instabilities at Fermilab

dipole, space-charge, coupling, quadrupole

633

T. Zolkin
University of Chicago, Chicago, Illinois, USA

The transverse beam dynamics in Fermilab Recycler ring has been analyzed using SCHARGEV Vlasov solver. In the first part of paper we discuss how SCHARGEV analyses collective instabilities for Gaussian bunch with strong space charge in resistive impedance environment. In the second part the bunched beam dynamics is studied depending on head-tail phase and damper gain. An example for Fermilab Recycler is presented.

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MOPMA056

Measurement and Modeling of Single Bunch Wake Field Effects in CESR

emittance, simulation, wakefield, storage-ring

681

J.R. Calvey, M.G. Billing, W. Hartung, J.D. Perrin, D. L. Rubin, D. Sagan, S. Wang
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work supported by NSF PHY-1416318 and NSF DMR 1332208. This research used the National Energy Research Scientific Computing Center, which is supported by DOE Contract No. DE-AC02-05CH11231.
Short-range wake fields have been incorporated into a Bmad-based particle tracking code in order to assess their contribution to current-dependent emittance growth, tune shift, and single bunch instabilities. The wakes are computed for CESR vacuum components using the T3P modeling software. Simulation results are compared with measurements of bunch length, vertical beam size, and coherent tune shift. Additionally, we use insertable scrapers to vary the transverse wake and measure the effect on the beam. We show that a vertical emittance increase at high current may be due to a transverse monopole wake, originating in the lump pump slots throughout CESR.

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MOPMA060

Impedance Measurement for the SPEAR3 Storage Ring

lattice, storage-ring, vacuum, damping

694

X. Huang, J.J. Sebek
SLAC, Menlo Park, California, USA

We studied the transverse impedance of the SPEAR3 storage ring with tune shift vs. beam intensity, head-tail instability and transverse mode coupling instability measurements. By taking measurements under different machine conditions, we probed the frequency dependence of the impedance, from which an impedance model was built. This model is consistent with instability measurements and previous bunch lengthening results.

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MOPMN004

CSR Impedance for Non-Ultrarelativistic Beams

wakefield, radiation, space-charge, synchrotron

709

R. Li
JLab, Newport News, Virginia, USA
C.-Y. Tsai
Virginia Polytechnic Institute and State University, Blacksburg, Virginia, USA

Funding: This work is supported by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
For the analysis of the coherent synchrotron radiation (CSR) induced microbunching gain in the low energy regime, such as when a high-brightness electron beam is transported through a low-energy merger in an energy-recovery linac (ERL) design, it is necessary to extend the CSR impedance expression in the ultrarelativistic limit to the non-ultrarelativistic regime. This paper presents our analysis of CSR impedance for general beam energies.

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MOPMN019

Understanding the Effect of Space Charge on Instabilities

space-charge, synchrotron, hadron, operation

743

M. Blaskiewicz
BNL, Upton, Long Island, New York, USA
A. Chao
SLAC, Menlo Park, California, USA
Y.H. Chin
KEK, Ibaraki, Japan

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The combined effects of space charge and wall impedance on transverse instabilities is an important consideration in the design and operation of hadron machines as well as an intrinsic academic interest. This study explores the combined effects of space charge and wall impedance using various simplified models in an attempt to produce a better understanding of their interplay.

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MOPMN020

Longitudinal Impedance of RHIC

synchrotron, experiment, storage-ring, scattering

746

M. Blaskiewicz, J.M. Brennan, K. Mernick
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
The longitudinal impedance of the two RHIC rings has been measured using the effect of potential well distortion on longitudinal Schottky measurements. With Z/n about 5 Ω the impedance of the yellow ring is roughly twice that of the blue ring.

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MOPMN021

NSLS-II Storage Ring BPM Button Development

vacuum, simulation, multipole, storage-ring

748

A. Blednykh, B. Bacha, G. Bassi, W.X. Cheng, C. Hetzel, B.N. Kosciuk, D. Padrazo, O. Singh
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract DE-AC02-98CH10886
The NSLS-II BPM Button design and its development process have been described. Subjects discussed include BPM Button impedance optimization, design and construction, production, BPM Button selection and a first temperature measurements at 200mA average current within 1200 bunches.

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MOPMN025

Local Impedance Estimation of NSLS-II Storage Ring with Bumped Orbit

closed-orbit, wiggler, damping, vacuum

754

J. Choi, G. Bassi, A. Blednykh, Y. Hidaka
BNL, Upton, Long Island, New York, USA

Funding: DOE contract No: DE-AC02- 98CH10886
As the newly constructed 3rd generation light source, NSLS-II is expected to provide the synchrotron radiation of ultra high brightness and flux with advanced insertion devices. To minimize the beam emittance, damping wigglers are used and the small aperture is located at the straight section with the damping wiggler and the corresponding vacuum camber is NEG coated. We used the local bump method to find the effect on the beam from the narrow aperture and the paper shows the results.

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MOPTY001

Development of Wideband BPM for Precise Measurement of Internal Bunch Motion

coupling, feedback, synchrotron, network

937

K.G. Nakamura
Kyoto University, Kyoto, Japan
Y.H. Chin, T. Koseki, T. Obina, M. Okada, M. Tobiyama, T. Toyama
KEK, Ibaraki, Japan
Y. Shobuda
JAEA/J-PARC, Tokai-Mura, Naka-Gun, Ibaraki-Ken, Japan

Funding: This work was supported by MEXT KAKENHI Grant Number 25105002, Grant-in-Aid for Scientific Research on Innovative Areas titled “ Unification and　Development of the Neutrino Science Frontier”
To suppress intra-bunch oscillations and to reduce particle losses, the intra-bunch feedback (IBFB) system has been developed in 2014 for the J-PARC Main Ring (MR). A new BPM was also installed to the MR for the IBFB system. This BPM has a sufficient frequency response and position sensitivity(up to 1.5GHz within 15% fluctuation ). However, a better performance may be needed in future for more precise analysis of internal motions (e.g. due to an electron cloud). We report the development of the BPM and precise measurement results of the BPM characteristics. We also report simulation studies of the digital equalizer which helps to reconstructs the beam shape from beam signals.

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MOPTY019

Precise Position Measurement by Analyzing the Correlation Between Electrodes of a Single Bpm

simulation, pick-up, hardware, synchrotron

975

Z.C. Chen
SSRF, Shanghai, People's Republic of China
L.W. Lai, Y.B. Leng, Y.B. Yan
SINAP, Shanghai, People's Republic of China

Beam position is one of the most important parameters in a particle accelerator. The more accurate and precise the measurement system is, the more features of the beam dynamics could be revealed. A method called model-independent analysis (MIA) takes advantage of multiple beam position monitors (BPM) on the storage ring to obtain the actual beam positions by removing the random noise of each BPM. Inspired by MIA, the original voltage waveforms obtained from the electrodes of a single BPM can also be decomposed to get the beam position information. This article discusses the results of the experiments and the evaluation of the performance of the BPM at the Shanghai Institute of Applied Physics.

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MOPTY033

Fast Kicker

kicker, simulation, vacuum, magnet-design

1001

V.V. Gambaryan, A.A. Starostenko
BINP SB RAS, Novosibirsk, Russia

Pulsed deflecting magnet project was worked out in BINP. The kicker design task is: impulsive force value is 1 mT*m, pulse edge is 5 ns, and impulse duration is about 200 ns. The unconventional approach to kicker design was offered. The possibility for set of wires using instead of plates using is considered. This approach allows us to reduce the effective plate surface. In this case we can decrease effects related to induced charges and currents. In the result of modelling optimal construction was developed. It includes 6 wires. The magnet aperture is about 5 cm. Calculated field rise time (about 1.5 ns) satisfies the conditions. Induced current effect reducing idea was confirmed. For configuration with 3 wires pair (with cross section of 2 mm) induced current in one wire is about 10% and in the wall is about 40%. However for design with plates current is about 40% and 20% respectively. Obtained magnet construction allows controlling of high field homogeneity by changing currents magnitudes in wires. In general we demonstrated the method of field optimization. Optimal kicker design was obtained. Wires using idea was substantiated.

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MOPTY041

Prototype Results with a Complete Beam Loss Monitor System Optimized for Synchrotron Light Sources

electron, detector, injection, electronics

1019

P. Leban
I-Tech, Solkan, Slovenia
K.B. Scheidt
ESRF, Grenoble, France

Beam loss monitors in synchrotron light sources are finding an increasing utility in particular with the trend of numerous light sources pushing to lower emittances and thus higher intra-beam scattering, while operating in top-up injection modes and employing in-vacuum undulators in their rings. The development of an optimized electron BeamLoss Monitor aims at fulfilling, in one single system, all possible functionalities and applications like both the measurement of fast-time-resolved losses at injection and the possibility of ultra-sensitive detection of low & slow electron loss level variations. This optimized beam loss monitor system comprises both the acquisition electronics and up to four sensor head per unit. The sensor heads themselves, that can be configured for different sizes or volumes, are based on the detection of the electromagnetic shower resulting from an electron loss through the use of either Cherenkov radiator or gamma scintillator and a photomultiplier tube, all assembled in a single compact housing ready for installation.

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MOPTY053

Electromagnetic Design and Optimization of Directivity of Stripline Beam Position Monitors for the High Luminosity Large Hadron Collider

luminosity, simulation, hadron, collider

1051

D. Draskovic, C.B. Boccard, O.R. Jones, T. Lefèvre, M. Wendt
CERN, Geneva, Switzerland

This paper presents the preliminary electromagnetic design of a stripline Beam Position Monitor (BPM) for the High Luminosity program of the Large Hadron Collider (HL-LHC) at CERN. The design is fitted into a new octagonal shielded Beam Screen for the low-beta triplets and is optimized for high directivity. It also includes internal Tungsten absorbers, required to reduce the energy deposition in the superconducting magnets. The achieved broadband directivity in wakefield solver simulations presents significant improvement over the directivity of the current stripline BPMs installed in the LHC.

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MOPWI012

Conceptual Design and Analysis of a Storage Ring Beam Position Monitor for the APS Upgrade

vacuum, operation, simulation, alignment

1170

B.K. Stillwell, R.M. Lill, R.R. Lindberg, M.M. O'Neill, B.G. Rocke, X. Sun
ANL, Argonne, Ilinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Created by UChicago Argonne, LLC, operator of Argonne National Laboratory, a U.S. Department of Energy Office of Science laboratory operated under Contract No. DE-AC02-06CH11357.
A conceptual design has been developed for a radio frequency (rf) pickup-type beam position monitor (BPM) for use in a multi-bend achromat (MBA) storage ring under consideration by the APS Upgrade project (APS-U). Beam feedback systems are expected to require fourteen rf BPMs per sector with exceptional sensitivity and mechanical stability. Simultaneously, BPM insertion length must be minimized to allow lattice designers the greatest freedom in selecting magnet lengths and locations. Envisioned is a conventional four probe arrangement integrated inside of a pair of rf-shielded bellows for mechanical isolation. Basic aspects of the design are presented along with the results of analyses which establish expected mechanical, electronic, and beam physics-related performance measures.

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TUAB2

First Collective Effects Measurements in NSLS-II with ID's

lattice, vacuum, quadrupole, storage-ring

1332

A. Blednykh, B. Bacha, G. Bassi, W.X. Cheng, J. Choi, Y. Hidaka, Y. Li, B. Podobedov, T.V. Shaftan, V. Smalyuk, T. Tanabe, G.M. Wang, F.J. Willeke, L.-H. Yu
BNL, Upton, Long Island, New York, USA

Funding: Work supported by DOE contract DE-AC02-98CH10886.
As another important milestone towards the final goal to store an average current of 500mA, the average current of 200mA, distributed within ~1000 bunches, was recently achieved in the NSLS-II storage ring after the installation of three Damping Wigglers and four In-Vacuum Undulators. First measurements of the collective effects and instability thresholds, both in single- and multi-bunch mode, are discussed.

Slides TUAB2 [2.691 MB]

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TUPJE065

Multi-Bunch Stability Analysis of the Advanced Photon Source Upgrade Including the Higher-Harmonic Cavity

HOM, damping, simulation, radiation

1784

L. Emery, T.G. Berenc, M. Borland, R.R. Lindberg
ANL, Argonne, Ilinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357
Multi-bunch stability simulations were done for the very-low-emittance hybrid seven-bend-achromat (H7BA) lattice proposed for the Advanced Photon Source (APS) upgrade. The simulations, performed using tracking code elegant, were meant to determine whether the long-term wakefields of the higher-order modes (HOMs) of the main 352-MHz cavities will produce an instability. The multi-particle simulations include the important effects of the Higher-Harmonic Cavity (HHC) and the longitudinal impedance of the new vacuum chamber. These realistic simulations show that the HHC provides additional damping in the form of the Landau damping. Still, the HOMs may likely produce a multi-bunch instability which can be cured with more effective HOM damping or a longitudinal feedback system.

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TUPJE069

Fast Injection System R&D for the APS Upgrade

kicker, high-voltage, injection, extraction

1797

F. Lenkszus, J. Carwardine, A.R. Cours, G. Decker, L.H. Morrison, X. Sun, J. Wang, F. Westferro, A. Xiao, C. Yao
ANL, Argonne, Ilinois, USA
A. Krasnykh
SLAC, Menlo Park, California, USA

Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
The MBA upgrade for the APS will operate with bunch swap out and on axis injection. The planned 324 bunch fill pattern places difficult demands on the injection and extraction kickers. The present concept uses dual stripline kickers driven by high Voltage pulsers. Minimizing perturbation on adjacent bunches requires very fast rise and fall times with relatively narrow ~20 nsec, 15 kV pulses. To achieve these requirements we have initiated a multifaceted R&D program. The R&D includes the HV pulser, stripline kicker and HV feedthrough. We have purchased a commercial dual channel HV pulser and are evaluating its performance and reliability. In addition, we are investigating the feasibility of using nonlinear ferrite loaded coaxial cables (shockwave transmission line) to sharpen the leading and trailing edges of high voltage pulses. We are also developing a prototype kicker and high voltage feedthrough. The requirements for injection and extraction, progress on prototype development and results of our HV pulser investigations will be reported.

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TUPJE076

Design Study of the Higher Harmonic Cavity for Advanced Photon Source Upgrade

cavity, operation, simulation, superconducting-cavity

1819

S.H. Kim, T.G. Berenc, J. Carwardine, G. Decker, M.P. Kelly, P.N. Ostroumov
ANL, Argonne, Illinois, USA

Funding: Results in this report are derived from work performed at Argonne National Laboratory. Argonne is operated by UChicago Argonne, LLC, for the U.S. Department of Energy under contract DE-AC02-06CH11357.
A higher-harmonic cavity is planned for the proposed Advanced Photon Source (APS) multi-bend achromat (MBA) lattice to increase the bunch length, improve the Touschek lifetime and increase the single-bunch current limit. We have investigated a range of options including 3rd, 4th, and 5th harmonics of the main radio frequency (RF) system, as well as configurations with and without external RF power couplers. The current baseline is a single 4th harmonic superconducting cavity with adjustable RF couplers and a slow tuner which provide the flexibility to operate over a wide range of beam currents. The cavity is designed to provide 0.84 MV at 1408 MHz for the nominal 6 GeV, 200 mA electron beam, and 4.1 MV main RF voltage. In this paper, we discuss the harmonic cavity parameters based on analytical calculations of the equilibrium bunch distribution and make comparisons to other options.

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TUPJE077

Instability Thresholds for the Advanced Photon Source Multi- Bend Achromat Upgrade

simulation, wakefield, injection, collective-effects

1822

R.R. Lindberg
ANL, Argonne, Illinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
An important operating mode for the multi-bend achromat (MBA) upgrade at the Advanced Photon Source (APS) calls for 200 mA average current divided evenly over 48 bunches. Ensuring that the desired 4.2 mA single bunch current can be stably stored requires a detailed understanding of the impedance in the MBA ring. We briefly discuss modeling sources of impedance using the electromagnetic codes GdfidL and ECHO, and how we then include both geometric and resistive wall wakefields using the tracking code elegant to predict collective instabilities. We first validate our procedures by comparing APS experimental measurements to tracking predictions using the APS storage ring impedance model. We then discuss the MBA impedance model, for which we find that a chromaticity of 5 units is sufficient to obtain the required 4.2 mA single bunch current. Finally, we mention certain design changes that may reduce the impedance and allow for a reduction in chromaticity.

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TUPJE078

Modeling of Impedance Effects for the APS-MBA Upgrade

vacuum, wakefield, photon, simulation

1825

R.R. Lindberg
ANL, Argonne, Illinois, USA
A. Blednykh
BNL, Upton, Long Island, New York, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357.
Understanding the sources of impedance is critical to accelerator design, and only becomes more important as vacuum chambers become smaller and closer to the electron beam. The multibend achromat upgrade at the Advanced Photon Source (APS) requires small, 22-mm diameter vacuum chambers and even smaller (6 mm) gaps for the insertion devices, so that both rf heating and wakefield-driven transverse instabilities become important concerns. We discuss modeling the primary sources of geometric impedance using the electromagnetic finite difference codes GdfidL and ECHO, and how these codes are influencing vacuum and accelerator component design.

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TUPJE079

High Charge Development of the APS Injector for an MBA Upgrade

booster, vacuum, ion, injection

1828

C. Yao, M. Borland, J.R. Calvey, K.C. Harkay, D. Horan, R.R. Lindberg, N. Sereno, H. Shang, X. Sun, J. Wang
ANL, Argonne, Illinois, USA

Funding: Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS MBA (multi-bend achromat) upgrade storage ring will employ a “swap out” injection scheme and requires a single-bunch beam with up to 20 nC from the injector. The APS injector, which consists of a 450-MeV linac, a particle accumulator ring (PAR), and a 7-GeV synchrotron (Booster), was originally designed to provide up to 6 nC of beam charge. High charge injector study is part of the APS upgrade R&D that explores the capabilities and limitations of the injector through machine studies and simulations, and identifies necessary upgrades in order to meet the requirements of the MBA upgrade. In the past year we performed PAR and booster high charge studies, implemented new ramp correction of the booster rap supplies, explored non-linear chromatic correction of the booster, etc. This report presents the results and findings.

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TUPMA007

Numerical Investigation of a Cascaded Longitudinal Space-Charge Amplifier at the Fermilab's Advanced Superconducting Test Accelerator

space-charge, radiation, bunching, simulation

1850

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

In a cascaded longitudinal space-charge amplifier (LSCA), initial density noise in a relativistic e-beam is amplified via the interplay of longitudinal space charge forces and properly located dispersive sections. This type of amplification process was shown to potentially result in large final density modulations * compatible with the production of broadband electromagnetic radiation. The technique was recently demonstrated in the optical domain **. In this paper we investigate, via numerical simulations, the performances of a cascaded LSCA beamline at the Fermilab's Advanced Superconducting Test Accelerator (ASTA). We especially explore the properties of the produced broadband radiation. Our studies have been conducted with an effective three-dimensional space-charge algorithm.
* Dohlus, M. et al. Proc. SPIE 8779. doi:10.1117/12.2017369
** Marinelli, A. et al. Phys. Rev. Lett. 110, 264802 (2013)

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TUPMA008

Numerical Study of Three Dimensional Effects in Longitudinal Space-Charge Impedance

space-charge, simulation, detector, radiation

1853

A. Halavanau, P. Piot
Northern Illinois University, DeKalb, Illinois, USA
P. Piot
Fermilab, Batavia, Illinois, USA

Longitudinal space-charge (LSC) effects are generally considered as detrimental in free-electron lasers as they can seed instabilities. Such "microbunching instabilities" were recently shown to be potentially useful to support the generation of broadband coherent radiation pulses. Therefore there has been an increasing interest in devising accelerator beamlines capable of sustaining this LSC instability as a mechanism to produce a coherent light source. To date most of these studies have been carried out with a one-dimensional impedance model for the LSC. In this paper we use a N-body "Barnes-Hut" algorithm * to simulate the 3D space charge force in the beam combined with Elegant ** and explore the limitation of the 1D model often used.
* Barnes, J. & Hut, P., Nature 324, 446-449, 1986.
** Borland, M., Advanced Photon Source LS-287, 2000.

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TUPMA041

On the Characterization of a CCR Source

brightness, radiation, FEL, emittance

1926

A.V. Smirnov
RadiaBeam, Santa Monica, California, USA

Funding: US Department of Energy, contract # DE- SC-FOA-0000760
Peak and spectral brightness of a resonant long-range wakefield extractor are evaluated. It is shown that the brightness is dominated by beam density within the slow wave structure and antenna gain of the outcoupling. Far field radiation patterns and brightness of circular and high-aspect-ratio planar radiators are compared. A possibility to approach the diffraction limited brightness is demonstrated. Role of group velocity in designing of the Cherenkov source is emphasized. The approach can be applied for design and characterization of various structure-dominated sources (e.g., wakefield extractors with gratings or dielectrics, or FEL-Cherenkov combined sources) radiating into a free space using an antenna (from microwave to far infra-red regions). The high group velocity structures can be also effective as energy dechirpers and for diagnostics of microbunched relativistic electron beams.

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TUPTY029

Collimation Cleaning at the LHC with Advanced Secondary Collimator Materials

collimation, simulation, scattering, proton

2068

E. Quaranta, R. Bruce, A. Mereghetti, S. Redaelli, A. Rossi
CERN, Geneva, Switzerland

The LHC collimation system must ensure efficient beam halo cleaning in all machine conditions. The first run in 2010-2013 showed that the LHC performance may be limited by collimator material-related concerns, such as the contribution from the present carbon-based secondary collimators to the machine impedance and, consequently, to the beam instability. Novel materials based on composites are currently under development for the next generation of LHC collimators to address these limitations. Particle tracking simulations of collimation efficiency were performed using the Sixtrack code and a material database updated to model these composites. In this paper, the simulation results will be presented with the aim of studying the effect of the advanced collimators on the LHC beam cleaning.

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TUPTY038

BPM Tolerances for HL-LHC Orbit Correction in the Inner Triplet Area

luminosity, optics, simulation, emittance

2094

M. Fitterer, R. De Maria
CERN, Geneva, Switzerland

Funding: The HiLumi LHC Design Study is partly funded by the European Commission within the Framework Programme 7 Capacities Specific Programme, Grant Agreement 284404.
For the HL-LHC beam spot sizes as small as 7 mum are considered for the high luminosity insertions IR1 and IR5. In addition, the luminosity has to be levelled over several hours by changing β^* resulting in constant changes of the optics and thus orbit changes. The small beam size and the continuous optics changes in general make the alignment of the beams at the IP challenging. In order to avoid continuous luminosity scans for the alignment of the beams at the IP, the orbit correction has to rely on the readings of the BPMs in the IT region. In this paper we review the requirements on resolution and accuracy of the BPMs and compare different options for the placement of the BPMs in the IT region.

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TUPTY051

Injection Protection Upgrade for the HL-LHC

injection, simulation, kicker, proton

2136

J.A. Uythoven, N. Biancacci, C. Bracco, L. Gentini, B. Goddard, A. Lechner, F.L. Maciariello, A. Perillo Marcone, B. Salvant, N.V. Shetty, G.E. Steele, F.M. Velotti
CERN, Geneva, Switzerland
O. Frasciello, M. Zobov
INFN/LNF, Frascati (Roma), Italy

The injector complex of the LHC is undergoing important changes in the light of the LIU project to provide brighter beams to the LHC. For this reason and as part of the High Luminosity LHC project the injection protection system of the LHC will be upgraded in the Long Shutdown 2 (2018 - 2019) to be able to protect downstream elements against injection failures with the high brightness, high intensity HL-LHC beams. The upgraded LHC injection protection system will consist of a segmented injection protection absorber TDIS, and auxiliary collimators and masks. The layout modifications are described, and the machine element protection and absorber jaw robustness studies are presented for the new systems.

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WEPWA046

Time Domain Simulations of Detuned Accelerating Cavities for Two Beam Applications

cavity, simulation, accelerating-gradient, cathode

2605

R.M. Jones, L.R. Carver
UMAN, Manchester, United Kingdom

A multi-harmonic accelerating cavity that has its fundamental and harmonic mode frequency detuned away from the bunch repetition frequency could provide the basis for a beam driven wakefield accelerator with high transformer ratios. The excitation of multiple harmonic eigenmodes will allow high gradients to be achieved without encouraging the onset of rf breakdown or pulsed surface heating. This accelerating cavity will be introduced, and time domain simulations verifying the theory will be shown.

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WEPMA008

RF Design of a High Gradient S-Band Travelling Wave Accelerating Structure for Thomx Linac

accelerating-gradient, linac, simulation, vacuum

2757

M. El Khaldi, L. Garolfi
LAL, Orsay, France

There is growing demand from the industrial and research communities for high gradient, compact RF accelerating structures. The Thomx high gradient structure (HGS) is travelling wave (TW), quasi constant gradient section and will operate at 2998.55 MHz (30°C in vacuum) in the 2π/3 mode. The optimization of the cell shape (Electromagnetic design) has been carried out with the codes HFSS and CST MWS, in order to improve the main RF characteristics of the cavity such as shunt impedance, accelerating gradient, group velocity, modified Poynting vector, surface fields, etc. Prototypes with a reduced number of cells have been designed. For an input power of about 20 MW, EM simulation results show that an average accelerating gradient of 28 MV/m is achieved which corresponds to a peak accelerating gradient of 35 MV/m, a peak surface gradient of 44 MV/m and peak modified Poynting vector S_cmax of 0.24 MW/mm².

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WEPMA013

Hom Damping Optimization Design Studies for BESSY VSR Cavities

damping, HOM, cavity, SRF

2774

A.V. Vélez, H.-W. Glock, J. Knobloch, A. Neumann
HZB, Berlin, Germany

The BESSY VSR project is a future upgrade of the 3rd generation BESSY II light source. By using the same "standard" user optics, simultaneously long (ca. 15ps) and short (ca. 1.5ps) bunches will be stored. Thus, superconducting higher harmonic cavities of the fundamental 500 MHz at two frequencies need to be installed in the BESSY II storage ring. This work describes the optimizations studies for the Waveguide-based HOM dampers and the adjustable fundamental power coupler for the 1.5 GHz first SRF cavity prototype.

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WEPMA017

Alvarez DTL Cavity Design for the UNLAC Upgrade

cavity, electron, DTL, simulation

2786

X. Du, L. Groening, S. Mickat
GSI, Darmstadt, Germany
A. Seibel
IAP, Frankfurt am Main, Germany

The 10⁸.4 MHz drift tube linac (DTL) accelerator for GSI’s UNLAC upgrade project is in its initial design stage using CST-MWS code. Optimization criteria for cavity design are effective shunt impedance (ZTT), transit-time factor, and electrical breakdown limit. In geometrical op-timization we have aimed at increase of the energy gain in each RF gap of the DTL cells by maximizing ZTT per peak surface field with special designed tube profile. Mul-ti-pacting probability is evaluated for one gap of typical single cell. For the beta profile design, a code based on VBA macros of CST is developed to perform cell by cell design with pre-optimized 3D tube structures. With this code several beta profile designs are presented and com-pared for the balance of power consumption, ZTT, tank length, and breakdown possibility of the complete cavity. The stability of the field has been taken into account and for this the crossed stem arrangement is assessed. This paper gives a short introduction of the method, presents some important results. Possible countermeas-ures are discussed.

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WEPMN012

Cathode Stalk Optimization for a 325 MHz Superconducting QWR Electron Gun

cathode, cavity, gun, electron

2940

P.L. Fan, Y.M. Li, L. Lin, K.X. Liu, S.W. Quan, F. Zhu
PKU, Beijing, People's Republic of China

Funding: Work supported by National Basic Research Project (No. 2011CB808302)
The structure of cathode stalk is very important for the performance of a superconducting QWR (Quarter Wave Resonator) gun. With improper design, RF power dissipation on the surface of cathode stalk and its surrounding tube can lead to a serious decrease of quality factor for superconducting QWR injector. We present here an optimized design of the cathode stalk for the 325 MHz superconducting QWR gun and special considerations are taken to minimize the power dissipation. The details of microwave simulation, beam dynamic simulation of the cavity with cathode stalks in different length, diameter and position are presented in this paper.

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WEPMN025

Harmonic Resonant Kicker Design for the MEIC Electron Circular Cooler Ring

cavity, electron, kicker, ion

2981

Y.L. Huang
IMP/CAS, Lanzhou, People's Republic of China
R.A. Rimmer, H. Wang, S. Wang
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S.DOE Contract No. DE-AC05-06OR23177.
Bunched-beam electron cooling of the high-energy ion beam emittance may be a crucial technology for the proposed Medium energy Electron Ion Collider (MEIC) to achieve its design luminosity. A critical component is a fast kicker system in the Circular Ring (CR) that periodically switches electron bunches in and out of the ring from and to the driver Energy Recovery Linac (ERL). Compared to a conventional strip-line type kicker, a quarter wave resonator (QWR) based deflecting structure has a much higher shunt impedance and so requires much less RF power. The cavity has been designed to resonate simultaneously at many harmonic modes that are integer multiples of the fundamental mode. In this way the resulting waveform will kick only a subset of the circulating bunches. In this paper, analytical shunt impedance optimization, the electromagnetic simulations of this type of cavity, as well as tuner and coupler concept designs to produce 5 odd and 5 even harmonics of 47.63MHz will be presented, in order to kick every 10th bunch in a 476.3 MHz bunch train.

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WEPMN047

Suppression of Higher Order Modes in an Array of Cavities Using Waveguides

HOM, damping, cavity, wakefield

3033

Ya.V. Shashkov, N.P. Sobenin
MEPhI, Moscow, Russia
M. Zobov
INFN/LNF, Frascati (Roma), Italy

Funding: Work is supported by Ministry of Education and Science grant 3.245.2014/r и and by the EU FP7 HiLumi LHC - Grant Agreement 284404
In the frameworks of the High Luminosity LHC upgrade program an application of additional harmonic cavities operating at multiplies of the main RF system frequency of 400 MHz is currently under discussion. A structure consisting of two 800 MHz single cell superconducting cavities with grooved beam pipes coupled by drift tubes has been suggested for implementation. However, it is desirable to increase the number of single cells installed in one cryomodule in order to decrease the number of transitions between “warm” and “cold” parts of the collider vacuum chamber. Unfortunately it can lead to the appearance of higher order modes (HOM) trapped between the cavities. In order to solve this problem the methods of HOM damping with rectangular waveguides connected to the drift tubes were investigated and compared. In this paper we describe the results obtained for arrays of 2, 4 and 8 cavities.

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WEPMN058

Transverse Impedance Measurements and DC Breakdown Tests on the First Stripline Kicker Prototype for the CLIC Damping Rings

simulation, coupling, kicker, extraction

3058

C. Belver-Aguilar, A. Faus-Golfe
IFIC, Valencia, Spain
M.J. Barnes, H.A. Day
CERN, Geneva, Switzerland
A. Faus-Golfe
LAL, Orsay, France
F. Toral
CIEMAT, Madrid, Spain

A first stripline kicker prototype for beam extraction from the CLIC Damping Rings (DRs) has been designed at IFIC and CIEMAT, with excellent field homogeneity, good power transmission and low beam coupling impedance. The prototype has been built by the company Trinos Va\-cuum Projects, and laboratory tests and measurements have been carried out at CERN to characterize, without beam, the electromagnetic response of the striplines. In this paper, we present the measurements of the transverse beam coupling impedance, using the coaxial wire method, and a comparison with simulations. Furthermore, results of DC breakdown tests, using High Vol\-ta\-ge (HV) power supplies, are also reported.

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WEPMN070

Measurement Techniques and Application of Combined Parallel/Orthogonal Magnetic Bias on a Ferrite Tuned Resonator in Low Frequency Range (3-10 MHz)

cavity, solenoid, power-supply, network

3087

G. Favia, F. Caspers, M. Morvillo, C. Rossi, C. Vollinger
CERN, Geneva, Switzerland

We present several measurement methods for evaluation of magnetic properties of magnetically biased and non-biased ferrite samples in a coaxial test fixture. One important aspect is the crosscheck of results obtained by using different and independent measurement and evaluation methods. Since a rather high DC bias current has to be applied, a dedicated network was designed that allows the passage of up to 50 A DC without degradation of the RF performance. With a combination of calibration methods and a compensating topology with two identical sample holders, a good performance was achieved. In this context, magnetic material parameters for about 10 different types of ferrite were obtained. The orthogonal magnetic bias was added by placing the entire test fixture into a large toroidal coil. Thus, the bias field can be supplied independently from, and in addition to the classical parallel bias. An optimal combination between the two biasing fields was found, resulting in a reduction of magnetic losses up to 50% on certain ferrites. We show that the mixed magnetization, normally used for garnets only, is beneficial also for other types of ferrites.

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WEPHA002

Electromagnetic Characterization of NEG Properties Above 200 GHz for the CLIC Damping Rings

simulation, damping, network, electron

3097

E. Koukovini-Platia, G. Iadarola, G. Rumolo, C. Zannini
CERN, Geneva, Switzerland

Non-Evaporable Getter (NEG) will be used in the CLIC electron damping rings (EDR) to suppress fast beam ion instabilities due to its effective pumping ability. The electromagnetic (EM) characterization of the NEG properties up to high frequencies is required for the correct impedance modeling of the DR components. The properties are determined using WR-3.4 and WR-1.5 rectangular waveguides, based on a combination of experimental measurements of the complex transmission coefficient S21 with a Vector Network Analyzer (VNA) and CST 3D EM simulations, for the frequency range of 220-330 GHz and 500-750 GHz. The results obtained using NEG-coated Aluminum (Al) waveguides are presented in this paper.

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WEPHA005

Characterization of the RF Fingers Contact Force for the LHC Warm Vacuum Bellow Modules

vacuum, alignment, operation

3106

C. Blanch Gutiérrez, V. Baglin, G. Bregliozzi, P. Chiggiato, R. Kersevan
CERN, Geneva, Switzerland

Along the 27 Km of LHC beam pipe, various types of vacuum bellow modules are needed to compensate the mechanical misalignments of the vacuum chambers during installation and to absorb their thermal expansion during the bake-out. In order to reduce the beam impedance during operation with beams these modules are equipped with RF bridges to carry the image current. They are usually made out of a copper tube insert at one side and Cu-Be RF fingers at the other end of the module. A spring is used to keep the contact between the RF fingers and the tube insert. The geometry and the choice of this spring become critical to ensure a good electrical contact. In this paper, a description of the test bench used to measure the contact force together with the procedure applied and the measurements performed are given. A summary of the maximum radial and axial offsets between the RF fingers and the insert tube while keeping a good electrical contact is presented.

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WEPHA025

Design of a Variable X-band RF Power Splitter

network, polarization, operation, scattering

3167

H. Zha, A. Grudiev, D. Gudkov, I. Syratchev
CERN, Geneva, Switzerland

The design of a two output ports, high power X-Band RF splitter with arbitrary split ratio is presented. This ratio is adjusted by mechanical changing the position a special RF short circuit piston. The piston is mounted on a step-motor providing the precise movement. Special measures were taken in the design to decrease the maximum electrical field on the cooper surface, as well as to maximise the bandwidth of the device. This splitter will be tested in the high power X-band test stand at CERN.

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WEPTY014

Development of Fast Kickers for the APS MBA Upgrade

kicker, simulation, high-voltage, injection

3286

C. Yao, J. Carwardine, A.R. Cours, F. Lenkszus, R.R. Lindberg, L.H. Morrison, X. Sun, J. Wang, F. Westferro, A. Xiao
ANL, Argonne, Illinois, USA

Funding: *Work supported by the U.S. Department of Energy, Office of Science, under Contract No. DE-AC02-06CH11357.
The APS multi-bend achromat (MBA) upgrade storage ring will support two bunch fill patterns: a 48-singlets and a 324-singlets. A “swap out” injection scheme is adopted. In order to minimize the beam loss and residual oscillation of injected beam and to minimize the perturbation of stored beam during a swap-on injection, the rise, fall, and flat-top parts of the kicker pulse must be held within a 22.8-ns interval. Traditional ferrite-core-type kickers can’t meet the timing requirements; therefore, we decided to use stripline-type kickers. We have completed a preliminary design of a prototype kicker geometry. Procurement of the pulser supply and other components of an evaluation system is under way. We report the specification and design of the fast kicker and current status.

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WEPTY016

RF Modeling of a Helical Kicker for Fast Chopping

kicker, simulation, experiment, linac

3293

M.H. Awida, A.Z. Chen, T.N. Khabiboulline, G.W. Saewert, V.P. Yakovlev
Fermilab, Batavia, Illinois, USA

High intensity proton particle accelerators that supports several simultaneous physics experiments requires sharing the beam. A bunch by bunch beam chopper system located after the Radio Frequency Quadrupole (RFQ) is required in this case to structure the beam in the proper bunch format required by the several experiments. The unused beam will need to be kicked out of the beam path and is disposed in a beam dumb. In this paper, we report on the RF modeling results of a proposed helical kicker. Two beam kickers constitutes the proposed chopper. The beam sequence is formed by kicking in or out the beam bunches from the streamline. The chopper was developed for Project X Injection Experiment (PXIE).

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WEPTY027

Kicker Pulsers for Recycler Nova Upgrades

cathode, kicker, high-voltage, controls

3324

C.C. Jensen
Fermilab, Batavia, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
An upgrade of the Recycler injection kicker system required a faster rise time pulser. This system required a field rise and fall time of < 57 ns and a field flattop of 1.6 μs. This paper describes the variety of improvements made over the years that have resulted in this latest thyratron pulser. The effects of the trigger, the reservoir and the load impedance on delay and rise time will be discussed.

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WEPTY044

Phase Transients in the Higher-Harmonic RF Systems For the ALS-U Proposal

simulation, experiment, beam-loading, synchrotron

3372

J.M. Byrd, S. De Santis, T.H. Luo, C. Steier
LBNL, Berkeley, California, USA

Funding: This work was supported by the Laboratory Directed Research and Development Program of Lawrence Berkeley National Laboratory under U.S. Department of Energy Contract No. DE-AC02-05CH11231.
The ALS upgrade proposal (ALS-U) requires lengthening the bunch by a factor of at least four in order to increase the beam lifetime to acceptable values. Due to the presence of gaps in the fill pattern, required by the injection/extraction kicker system, the beam-induced voltage in the passive, normal-conducting, cavities which we plan to use is not constant over the length of a bunch train. We present our result on the optimal tuning of the harmonic cavities to obtain the best lifetime increase, including the effects of strongly non-gaussian bunch shapes and wakefield distortions of the potential well.

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WEPTY051

Stripline Kicker for Integrable Optics Test Accelerator

kicker, proton, electron, operation

3390

S. A. Antipov
University of Chicago, Chicago, Illinois, USA
A. Didenko, V.A. Lebedev, A. Valishev
Fermilab, Batavia, Illinois, USA

Funding: Fermilab is operated by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the United States Department of Energy.
We present a design of a stripline kicker for Integrable Optics Test Accelerator (IOTA). For its experimental program IOTA needs two full-aperture kickers, capable to create an arbitrary controllable kick in 2D. For that reason their strengths are variable in a wide range of amplitudes up to 16 mrad, and the pulse length 100 ns is less than a revolution period for electrons. In addition, the kicker has a physical aperture of 40 mm for a proposed operation with proton beam, and an outer size of 70 mm to fit inside existing quadrupole magnets to save space in the ring. Computer simulations using CST Microwave Studio show high field uniformity and wave impedance close to 50 Ω.

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WEPTY056

Novel High Power Sources for the Physics of Ionospheric Modification

gun, cathode, simulation, electron

3398

B. Beaudoin, T.M. Antonsen, I. Haber, T.W. Koeth, A.H. Narayan, G.S. Nusinovich, K.J. Ruisard
UMD, College Park, Maryland, USA
J. Rodgers
Naval Research Laboratory (NRL), Washington, USA

Funding: This work is supported by the Air Force Office of Scientific Research under grant FA95501410019.
The ionosphere plays a controlling role in the performance of critical civilian and DoD systems including the ELF-ULF communications. The objective of Ionospheric Modification is to control triggered processes to improve the performance of trans-ionospheric C3I systems and develop new applications that take advantage of the ionosphere as an active plasma medium. A key instrument is the Ionospheric Heater, a powerful HF transmitter that modifies the properties of the ionospheric plasma by modulating the electron temperature at preselected altitudes. A major reason for the development of a mobile source is that it would allow investigators to conduct the needed research at different latitudes without building permanent installations. As part of a MURI, UMD will develop a powerful RF source utilizing IOT technology in class-D amplifier mode. This technology was chosen because it has the potential to operate at very high efficiency. Some of the technical challenges presented in this paper will include a gun design that minimizes intercepted current, a compact tunable cavity, an efficient modulator system capable of modulating a high power beam and output couplers to feed the antennas.

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WEPTY063

Co-Linear X-Band Energy Booster (XCEB) Cavity and RF System Details

cavity, electron, extraction, linac

3421

T. Sipahi, S. Biedron, S.V. Milton
CSU, Fort Collins, Colorado, USA

Due to their higher intrinsic shunt impedance X-band accelerating structures offer significant gradients with relatively modest input powers. At the Colorado State University Accelerator Laboratory (CSUAL) we would like to adapt this technology to our 1.3-GHz, L-band accelerator system in order to increase our overall beam energy in a manner that does not require investment in an expensive, custom, high-power X-band klystron system. Here we provide the design details of the X-band structures that will allow us to achieve our goal of reaching the maximum practical net potential across the X-band accelerating structure while driven solely by the beam from the L-band system.

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WEPTY071

Time Resolved Cryogenic Cooling Analysis of the Cornell Injector Cryomodule

HOM, simulation, cryogenics, operation

3443

R.G. Eichhorn, S.R. Markham, P. Quigley, E.N. Smith
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Managing parallel cryogenic flows has become a key challenge in designing efficient and smart cryo-modules for particle accelerators. In analyzing the heating dynamics of the cornell high current injector module a power-full computational tool has been set-up allowing time resolved analysis and optimization. We will describe the computational methods and data sets we have used, report the results and compare them to measured data from the module being in good agreement. Mitigation strategies developed on basis of this model have helped pushing the operational limitations.

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WEPTY083

Five-cell Superconducting RF Module with a PBG Coupler Cell: Design and Cold Testing of the Copper Prototype

HOM, cavity, factory, damping

3475

S. Arsenyev, D.Y. Shchegolkov, E.I. Simakov
LANL, Los Alamos, New Mexico, USA
C.H. Boulware, T.L. Grimm, A. Rogacki
Niowave, Inc., Lansing, Michigan, USA

We report the design and experimental data for a copper prototype of a superconducting radio-frequency (SRF) accelerator module. The five-cell module has an incorporated photonic band gap (PBG) cell with couplers. The purpose of the PBG cell is to achieve better higher order mode (HOM) damping which is vital for preserving the quality of highcurrent electron beams. Better HOM damping raises the current threshold for beam instabilities in novel SRF accelerators. The PBG design also increases the real-estate gradient of the linac because both HOM damping and the fundamental power coupling can be done through the PBG cell instead of on the beam pipe via complicated end assemblies. First, we will discuss the design and accelerating properties of the structure. The five-cell module was optimized to provide good HOM damping while maintaining the same accelerating properties as conventional elliptical-cell modules. We will then discuss the process of tuning the structure to obtain the desired accelerating gradient profile. Finally, we will list measured quality factors for the accelerating mode and the most dangerous HOMs.

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WEPWI030

Injector Cavities Fabrication, Vertical Test Performance and Primary Cryomodule Design

cavity, cryomodule, HOM, dipole

3551

H. Wang, G. Cheng, W.A. Clemens, G.K. Davis, K. Macha, R.B. Overton, D. Spell
JLab, Newport News, Virginia, USA

Funding: Authored by Jefferson Science Associates, LLC under U.S. DOE Contract No. DE-AC05-06OR23177.
After the electromagnetic design * and the mechanical design ** of a β=0.6, 2-cell elliptical SRF cavity, the cavity has been fabricated. Then both 2-cell and 7-cell cavities have been bench tuned to the target values of frequency, coupling external Q and field flatness. After buffer chemistry polishing (BCP) and high pressure rinses (HPR), Vertical 2K cavity test results have been satisfied the specifications and ready for the string assembly. We will report the cavity performance including Lorenz Force Detuning (LFD) and Higher Order Modes (HOM) damping data. Its integration with cavity tuners to the cryomodule design will be reported.
* H. Wang, etc., Proceeding of IPAC2013, Shanghai, China, WEPWO073.
** G. Cheng, etc., Proceeding of PAC2013, Pasadena, CA, WEPAC47.

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WEPWI037

Imperfection and Tolerance Analysis of HOM Couplers for ODU/SLAC 400 MHz Crabbing Cavity

HOM, cavity, dipole, luminosity

3572

S.U. De Silva, J.R. Delayen, H. Park
ODU, Norfolk, Virginia, USA
Z. Li
SLAC, Menlo Park, California, USA
R.G. Olave
Old Dominion University, Norfolk, Virginia, USA

In preparation for the LHC High Luminosity upgrade, a 400 MHz crab cavity has been developed jointly at ODU/SLAC, including two higher order mode couplers designed to dampen the wakefields in order to comply with the impedance budget specified for the LHC system. During fabrication, assembly, and processing of the couplers, a number of imperfections may arise that could modify the higher order mode spectrum and the associated impedance for each mode. We present here a detailed study of the imperfections of the horizontal- and vertical- HOM couplers, and the associated allowed tolerances for manufacture, assembly and processing.

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WEPWI054

Design and Test of the RHIC CMD10 Abort Kicker

kicker, vacuum, network, coupling

3612

H. Hahn, M. Blaskiewicz, K.A. Drees, W. Fischer, W. Meng, J.-L. Mi, C. Montag, C. Pai, J. Sandberg, N. Tsoupas, J.E. Tuozzolo, W. Zhang
BNL, Upton, Long Island, New York, USA

Funding: Work supported by Brookhaven Science Associates, LLC under Contract No. DE-AC02-98CH10886 with the U.S. Department of Energy.
Planned and unplanned thyratron pre-fire triggered beam dumps have been observed in the yellow ring that were associated with quenches of the superconducting main ring magnets as the proton intensities increased in the FY10¹³ run. The increasing vacuum level indicated beam induced kicker ferrite heating causing lower magnetic kick field at a nominal pulse current. In anticipation of higher current and shorter bunches in FY2015 an accelerator improvement program was initiated to reduce the longitudinal coupling impedance with changes to the eddy-current strip geometry using Opera simulations and to change the CMD5005 to CMD10 ferrite. Results of the standard impedance measurements and of pulse current in heating tests to 170 °C are reported. All 10 dump kickers are being modified and are encapsulated with a cooling system for installation in the rings.

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WEPWI059

Higher Order Mode Filter Design for Double Quarter Wave Crab Cavity for the LHC High Luminosity Upgrade

HOM, cavity, luminosity, coupling

3627

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J. Skaritka, S. Verdú-Andrés, Q. Wu
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
G. Burt, B.D.S. Hall
Cockcroft Institute, Lancaster University, Lancaster, United Kingdom
G. Burt
Lancaster University, Lancaster, United Kingdom
R. Calaga, O. Capatina
CERN, Geneva, Switzerland
T.J. Jones
STFC/DL, Daresbury, Warrington, Cheshire, United Kingdom

Funding: Work partly supported by US LARP, by US DOE under contract No. DE-AC02-05CH11231 and through BSA under contract No. DE-AC02-98CH10886. Research supported by EU FP7 HiLumi LHC - Grant Agreement 284404.
A double quarter wave crab cavity (DQWCC) was designed for the Large Hadron Collider (LHC) luminosity upgrade. A compact Higher Order Mode (HOM) filter with wide stop band at the deflecting mode is developed for this cavity. Multi-physics finite element simulation results are presented. The integration of this design to the cavity cryomodule is described.

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WEPWI061

Design of Normal Conducting 704 MHz and 2.1 GHz Cavities for LEReC Linac

cavity, resonance, electron, simulation

3634

B. P. Xiao, S.A. Belomestnykh, I. Ben-Zvi, J.C. Brutus, A.V. Fedotov, G.T. McIntyre, K.S. Smith, J.E. Tuozzolo, Q. Wu, W. Xu, A. Zaltsman
BNL, Upton, Long Island, New York, USA
S.A. Belomestnykh, I. Ben-Zvi
Stony Brook University, Stony Brook, USA
V. Veshcherevich
Cornell University (CLASSE), Cornell Laboratory for Accelerator-Based Sciences and Education, Ithaca, New York, USA

Funding: Work is supported by Brookhaven Science Associates, LLC under contract No. DE-AC02-98CH10886 with the US DOE.
To improve RHIC luminosity for heavy ion beam energies below 10 GeV/nucleon, the Low Energey RHIC electron Cooler (LEReC) is currently under development at BNL. Two normal conducting cavities, a single cell 704 MHz cavity and a 3 cell 2.1 GHz third harmonic cavity, will be used in LEReC for bunch stretching and energy spread correction. In this paper we report the design of these two cavities.

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THPF027

Ten Gap Model of a New Alvarez DTL Cavity at GSI

simulation, cavity, ion, DTL

3748

A. Seibel, O.K. Kester
IAP, Frankfurt am Main, Germany
X. Du, L. Groening, S. Mickat
GSI, Darmstadt, Germany

In order to meet the challenges of the FAIR project at GSI requiring highest beam intensities an upgrade of the existing Universal Linear Accelerator (UNILAC) is planned. The 10⁸ MHz cavities will be replaced by new rf-structures of the same frequency. Simulations are done to improve the rf-properties. The geometry of the drift tubes is to be changed to a smoother curvature to reach a homogeneous surface field distribution and higher shunt impedances. To check the necessity of cooling channels, simulations on the temperature distribution at the drift tubes and stems are conducted. A test bench for low power rf-measurements with a 10 gap aluminum model (scale 1:3) is under construction. The modular mechanical design of the model will allow probing experimentally a wide range of drift tube and stem geometries. With the bead pull method the electrical field distribution will be measured as well as the field stability with respect to parasitic modes. Additionally, appropriate locations along the cavity to place fixed and dynamic rf-frequency tuners will be determined.

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THPF034

Injection Kicker for HESR at FAIR using Semi-Conductor Switches

injection, kicker, vacuum, antiproton

3770

R. Tölle, N. Bongers, F.M. Esser, R. Gebel, S. Hamzic, H. Jagdfeld, F. Klehr, B. Laatsch, L. Reifferscheidt, M. Retzlaff, L. Semke, H. Soltner, H. Stockhorst
FZJ, Jülich, Germany
S. Antoine, W. Beeckman, P. Bocher, O. Cosson, P. Jivkov, D. Ramauge
Sigmaphi, Vannes, France

The High Energy Storage Ring for Antiprotons is going to be built at FAIR in Darmstadt on the extended GSI campus. It will receive the antiprotons via the Collector Ring (CR). Using a barrier bucket, the circulating particles will be compressed into one half of the circumference. New particles have to be injected into the remaining half. Thus rise and fall time must not exceed 220 ns each with a flat top of 500 ns. A kick angle of 6.4 mrad is required at 13 Tm magnetic rigidity. The system must allow pole reversal for injection of positively charged particles. With a voltage lower than 40 kV a semi-conductor based pulser is going to be realized. Boundary conditions and the status of preparatory work are described. Simulation results and available measurements are presented.

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THPF049

The Simulation and Manufacture of the Room Temperature Cross-bar H Type Drift Tube Linac

cavity, DTL, proton, rfq

3811

J.H. Li
China Institute of Atomic Energy, Beijing, People's Republic of China
Z. Li
SCU, Chengdu, People's Republic of China

Funding: This work is supported by the National Natural Science Foundation of China (NSFC).
The room temperature Cross-bar H Type Drift Tube Linac (CH-DTL) is one of the candidate acceleration structures working in CW mode. In order to optimize the parameters, the 3 dimensional electromagnetic field of the CH-DTL cavity is simulated. The method of parameter sweeping with constraint variable is better than the method of parameter sweeping with only one variable during the optimization. In order to simplify the manufacture, the drift tube surface can be designed as spherical shape. The effective shunt impedance of the CH-DTL cavity with cylinder end cup is better than that with cone cup.

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